Black-Throated Green Warbler, Bay-Breasted Warbler and Cape May Warbler Conservation Management Plan 2014–2019 Alberta Species at Risk Conservation Management Plan No. 10
Black-Throated Green Warbler,
Bay-Breasted Warbler and Cape May Warbler
Conservation Management Plan
2014–2019
Alberta Species at Risk Conservation Management Plan No. 10
ii
Black-Throated Green Warbler,
Bay-Breasted Warbler and Cape May Warbler
Conservation Management Plan
2014–2019
Prepared by:
Samuel Haché
and
Theresa Hannah
March 2014
iii
ISBN: ISBN 978-1-4601-1625-8 (PDF)
Cover photos: Alberta Environment and Sustainable Resource Development
For copies of this report, contact:
Information Centre — Publications
Alberta Environment and Sustainable Resource Development
Main Floor, Great West life Building
9920–108 Street
Edmonton, Alberta, Canada T5K 2M4
Telephone: (780) 422-2079
OR
Visit the Species at Risk Program web site at:
http://esrd.alberta.ca/fish-wildlife/species-at-risk/default.aspx
This publication may be cited as:
Alberta Environment and Sustainable Resource Development. 2014. Black-throated
Green Warbler, Bay-breasted Warbler and Cape May Warbler Conservation Management
Plan 2014–2019. Alberta Environment and Sustainable Resource Development. Species
at Risk Conservation Management Plan No. 10. Edmonton, AB. 33 pp.
iv
PREFACE
Albertans are fortunate to share their province with a diversity of wild species. A small
number of these species are classified as Species of Special Concern because they have
characteristics that make them particularly sensitive to human activities or natural events.
Special conservation measures are necessary to ensure that these species do not become
Endangered or Threatened.
Conservation management plans are developed for Species of Special Concern to provide
guidance for land and resource management decisions that affect the species and their
habitat. These plans are intended to be a resource tool for Environment and Sustainable
Resource Development (ESRD) staff.
Conservation management plans provide background information including species
biology, threats to species and habitat, and inventory/monitoring history. Plans also
provide a goal, objectives, and actions (management recommendations). Management
recommendations are typically categorised into inventory and monitoring needs; habitat
management and conservation; education and communication; and additional
management considerations as required.
Conservation management plans are generally prepared by an ESRD biologist who has
been designated as the provincial species lead. Writers from outside ESRD are
occasionally sought to prepare plans for species for which there is little in-house
expertise. In order to ensure accuracy and utility, each plan is reviewed by a species
expert and designated provincial representatives from different ESRD programs. In some
cases there may be additional reviewers from staff, industry, and other agencies.
Conservation management plans are internal guidance documents. They are implemented
under the guidance of the species lead and are “living” documents that can be revised at
any time as required. Conservation management plans are more succinct than the
recovery plans that are prepared for Endangered and Threatened species and do not
involve participation of a multi-stakeholder team.
Conservation management plans are approved by the Director of Fish and Wildlife
Policy. Plans will be reviewed annually by the species lead and updated if necessary, and
a more in-depth review will occur five years after a plan’s approval.
v
EXECUTIVE SUMMARY
In Alberta, the black-throated green warbler (Setophaga virens) has been designated a
Species of Special Concern, and the bay-breasted warbler (Setophaga castanea) and Cape
May warbler (Setophaga tigrina) have been recommended for Species of Special
Concern status due to perceived population declines and projected future habitat loss. All
three species are neotropical migrants that breed in the Canadian boreal forest.
The black-throated green warbler is associated with old mixedwood and deciduous stands
and is considered a mature and interior forest species. The bay-breasted and Cape May
warblers are associated with old coniferous stands and are considered late-successional
forest specialists. All three species are sensitive to habitat loss, alteration, and
fragmentation; primary threats come from industrial activities. For successful
management of these species in Alberta, habitat requirements at both the stand and
landscape scales need to be considered. Habitat management for these warbler species
will benefit a variety of resident and migratory avian species.
This plan recommends various ways to conserve warbler populations and habitat,
including: long-term community-level surveys and detailed demographic studies;
maintaining old coniferous stands in large blocks with minimal edge (for bay-breasted
and Cape May warblers); maintaining old mixedwood forests with an overstory
composed of large white spruce and paper birch in large blocks with minimal edge (for
black-throated green warbler); using caution with spruce budworm control (bay-breasted
and Cape May warblers are considered spruce budworm specialists); and improved
collaboration with stakeholders and communication with the public. Integration of the
listed recommendations into current land management practices would help protect
habitat and favour conservation of these songbirds and other avian species.
ACKNOWLEDGEMENTS
We thank Dave Stepnisky (Alberta Fish and Wildlife) for reviewing this plan and
especially Lisa Wilkinson (Alberta Fish and Wildlife) for her guidance at each step
leading to the completion of this document. An earlier version of this plan was reviewed
by Lisa Mahon (Environment Canada). Sarah Rovang assisted with formatting, and
Nyree Sharp assisted with amalgamating the three warbler plans into one management
plan, and edited and formatted the final document.
vi
TABLE OF CONTENTS
PREFACE .......................................................................................................................... iv
EXECUTIVE SUMMARY ................................................................................................ v
ACKNOWLEDGEMENTS ................................................................................................ v
1.0 INTRODUCTION ..................................................................................................... 1
1.1 Distribution, Habitat Requirements and Breeding Biology .................................... 1
1.2 Population Trends ................................................................................................... 8
1.3 Threats to Populations ............................................................................................. 8
1.3.1. Forestry Sector .................................................................................................. 8
1.3.2. Energy Sector .................................................................................................. 10
1.3.3. Agriculture ...................................................................................................... 10
1.3.4. Natural Disturbances (insect outbreak and forest fire) ................................... 11
1.3.5. Urban Expansion ............................................................................................. 12
1.3.6. Winter and Migration Stopover Habitat ......................................................... 12
2.0 GOALS AND OBJECTIVES .................................................................................. 13
2.1 Goal ....................................................................................................................... 13
2.2 Objectives .............................................................................................................. 13
3.0 MANAGEMENT ACTIONS .................................................................................. 13
3.1 Monitoring and Assessment .................................................................................. 13
3.2 Habitat Conservation and Management ................................................................ 15
3.3 Research ................................................................................................................ 17
3.4 Education and Communication ............................................................................. 17
4.0 SUMMARY ............................................................................................................. 18
5.0 LITERATURE CITED ............................................................................................ 19
6.0 APPENDIX 1. POPULATION TRENDS ............................................................... 31
TABLE OF FIGURES
Figure 1. Black-throated green warbler distribution in Alberta. ......................................... 5
Figure 2. Bay-breasted warbler summer range in Alberta. ................................................. 6
Figure 3. Cape May warbler summer range in Alberta. ..................................................... 7
1
1.0 INTRODUCTION
The black-throated green warbler (Setophaga virens) has been designated a Species of
Special Concern in Alberta because of perceived population declines and projected future
habitat loss (Endangered Species Conservation Committee 2001). The bay-breasted
warbler (Setophaga castanea) and Cape May warbler (Setophaga tigrina) have been
recommended for Species of Special Concern status in Alberta for the same reasons
(Endangered Species Conservation Committee 2002a, 2002b). In the General Status of
Alberta Wild Species 2010, all three are classified as Sensitive (Alberta Environment and
Sustainable Resource Development 2012a).
These species are protected under both the federal Migratory Birds Convention Act and
Alberta’s Wildlife Act. At the federal level, they are considered as Secure (species that
show a trend of decline in numbers in Canada, but remain relatively widespread or
abundant; Environment Canada 2012a, b). About 98% and 99% of the Cape May and
Bay-breasted warblers’ breeding populations, respectively, are in Canada. The
International Union for Conservation of Nature (IUCN) Red List status for these species
is Least Concern, owing to large ranges and population sizes and slow declines (IUCN
2013).
Alberta’s Endangered Species Conservation Committee (ESCC) has made the following
recommendations for these three species (ESCC 2001, 2002a,b):
1. Designating the species as Species of Special Concern.
2. Developing mechanisms to identify and implement conservation and management
strategies for the three species.
3. Enhancing programs to collect information on each species’ population size,
distribution and trend. Reassessing the status of the species within five years.
4. Conserving and managing habitat for the three species.
5. Securing appropriate management strategy, including funding and personnel, for
conservation actions.
1.1 Distribution, Habitat Requirements and Breeding Biology
These three warbler species are neotropical migratory songbirds and members of the
Parulidae family. They arrive in Alberta in mid- to late May, and fall migration occurs
between mid-August and mid-September (Lesser Slave Lake Bird Observatory,
unpublished data). They spend 30–40% of their annual cycle on the breeding ground
(Morse and Poole 2005, Venier et al. 2011). Wintering grounds range from Mexico and
Central America (black-throated green; Morse and Poole 2005) to Central America and
northern South America (bay-breasted; Venier et al. 2011), and the Caribbean islands
(Cape May; Baltz and Latta 1998).
Black-throated green warbler
The breeding range includes the southern portion of the boreal, mixed and deciduous
forests of northeastern North America (Morse and Poole 2005). In Alberta, the breeding
2
range extends from the border with British Columbia to Cold Lake, and from Wood
Buffalo National Park to the lower Athabasca River drainage, with few records from the
northwest of the province (Fig. 1; see also Norton 1999, Alberta Biodiversity Monitoring
Institute 2012, Boreal Avian Modelling Project 2012a).
In western Canada, the black-throated green warbler occurs in spruce forests, mixedwood
stands dominated by large spruce (Salt 1973, Semenchuk 1992, Hobson and Bayne
2000a), and deciduous-dominated mixedwood forests (Robichaud and Villard 1999,
Hannah 2006) of the boreal mixedwood, boreal foothills, and boreal uplands ecoregions
(Strong and Leggat 1981). These stands are usually 100–130 years of age, with a canopy
composed of white spruce (Picea glauca), trembling aspen (Populus tremuloides) and
balsam poplar (Populus balsamifera; Hannah 2006). In Alberta, the highest densities of
black-throated green warbler have been recorded in closed mature mixedwood, open
mature deciduous, and closed young mixedwood stands (0.7–1/ha), and to a lesser extent
in closed mature coniferous stands (0.5/ha; density estimates for the Boreal Taiga Plains
Bird Conservation Region [BCR 6], Boreal Avian Monitoring Project 2012a). Estimates
of territory size range from 0.8 to 2.2 ha (F. Schmiegelow and T. Hannah, unpublish. data
cited by Norton 1999). As noted by Kirk et al. (2012), the species occurs in a wide
variety of forest types, but the contribution of the different stand types to overall
population viability is unclear. Nonetheless, the species has often been considered as an
indicator of mature forests, a mature forest specialist (Westworth and Telfer 1993, Kirk et
al. 1996, Schmiegelow and Hannon 1999, Venier and Pearce 2005, Zitske et al. 2011), a
forest interior specialist (Morse and Poole 2005, Villard et al. 2007, Kardynal et al.
2012), and a species sensitive to habitat alteration (Norton and Hannon 1997, Guénette
and Villard 2005, Atwell et al. 2008).
The black-throated green warbler forages mainly on insects, particularly caterpillars
(Bent 1953, Morse 1976) found in large diameter white spruce (diameter at breast height
[dbh] = ca. 50 cm; Robichaud and Villard 1999, Hannah 2006). Large white spruce (dbh
= ca. 50 cm) are also preferred as song posts. Paper birch (Betula papyrifera; dbh = ca.
20 cm) is the preferred nesting substrate, but other tree species including white spruce
and balsam poplar are also used (Robichaud and Villard 1999, Hannah 2006). The black-
throated green warbler builds an open-cup nest composed of twigs, grass, birch bark,
lichen and spider silk, located anywhere along a branch, or adjacent to the trunk and
usually between 1–3 m (but up to 20 m) from the ground (Morse and Poole 2005).
Generally, 3–5 eggs are laid and renesting attempts after failure have been documented
for this species (Morse and Poole 2005).
Bay-breasted warbler
During the breeding season, the bay-breasted warbler is associated with old coniferous
stands of the Canadian boreal forest. The range of this songbird in Alberta encompasses
most of the forested portion of the province, excluding the Rocky Mountains, and its
southern boundary corresponds with the southern limit of the Boreal Forest Natural
Region and Lower Foothills Natural Subregion (Fig. 2, see also Norton 2001a, Alberta
Biodiversity Monitoring Institute 2012, Boreal Avian Modelling Project 2012b).
3
Stands used by the bay-breasted warbler are usually dominated by white spruce or balsam
fir (Abies balsamea). Bogs, swamps, younger, more open stands, and mixedwood stands
can also be used (Venier et al. 2011), especially at high population levels of spruce
budworm (Choristoneura fumiferana; Venier et al. 2009, Venier and Holmes 2010). In
Alberta, the highest densities of territorial males (1/ha) have been reported in closed
mature coniferous stands and, to a lesser extent (0.1–0.3/ha), in open mature coniferous
and closed or young mixedwood stands composed of trembling aspen, balsam poplar, or
paper birch (density estimates for the Boreal Taiga Plains [BCR 6], Boreal Avian
Monitoring project 2012b). Hence, this species is considered a late-successional forest
specialist (Hobson and Bayne 2000a, Kirk and Hobson 2001, Rempel 2007). Negative
effects of habitat fragmentation have been reported for this species in many Canadian
provinces (Drolet et al. 1999, Hobson and Bayne 2000b, Rempel 2007), as have negative
effects of habitat alteration (Guénette and Villard 2005).
The bay-breasted warbler forages mainly on insects and spiders in conifer foliage
(Cumming 2004, Venier et al. 2011). While in the boreal forest, it forages intensively on
spruce budworms and forest tent caterpillars (Malacosoma disstria), which often leads to
large annual population fluctuations during infestations of these prey species (Venier and
Holmes 2010). Territory size is estimated at approximately 1.5 ha (Sabo 1980), but the
species can be gregarious in years of high food abundance (Venier et al. 2011). Typically,
the bay-breasted warbler builds open-cup nests about 5 m above the ground (range 1–20
m) in dense conifer trees, usually white spruce, and lays 5–6 eggs (range 3–7; reviewed
by Venier et al. 2011). Larger clutch sizes have been reported during insect outbreaks
(MacArthur 1958). There is no information available on renesting events for this species.
However, this behaviour is common in other warbler species and may be expected to
occur if the initial nesting attempt fails early in the breeding season (Morse and Poole
2005, Porneluzi et al. 2011).
Cape May warbler
The breeding range of the Cape May warbler covers most of the Canadian boreal forest
(Baltz and Latta 1998). In Alberta, the breeding range extends from Hinton to Cold Lake
in the south, occupying most forested areas of the province north to the border with the
Northwest Territories (Fig. 3; see also Alberta Biodiversity Monitoring Institute 2012,
Boreal Avian Modelling Project 2012c).
Throughout its breeding range, the Cape May warbler is associated with old coniferous
forests (Baltz and Latta 1998). The species is uncommon and locally distributed in
Alberta, as a result of its relatively narrow habitat requirements. It is found primarily in
pure stands of mature or old white spruce or fir (Abies spp.), and conifer-dominated
mixedwood stands composed of trembling aspen and paper birch (Semenchuk 1992).
Individuals sing, feed and nest high in the spruce canopy (Baltz and Latta 1998).
Territory size is estimated between 0.4–0.7 ha (Kendeigh 1947, Crawford and Jennings
1989). In Alberta, the highest densities of territorial males have been recorded in closed
mature coniferous stands (1/ha) and, to a lesser extent, in open mature coniferous and
open mixedwood stands (0.5–0.6/ha; density estimates for the Boreal Taiga Plains [BCR
6], Boreal Avian Monitoring project 2012c). This species has been considered a late-
4
successional forest specialist (Kirk and Hobson 2001) vulnerable to habitat loss,
alteration and fragmentation (A. J. Erskin, cited by Baltz and Latta 1998; Meiklejohn and
Hughes 1999).
The Cape May warbler forages mainly on caterpillars, beetles and spiders, from mature
spruces and firs (Baltz and Latta 1998). It has a unique semitubular tongue that allows for
the consumption of nectar and fruit during migration and winter months (Baltz and Latta
1998). The Cape May warbler is also considered a spruce budworm specialist. Indeed, the
annual variation in abundance of this prey has been shown to generate large fluctuations
in population size of the Cape May warbler (reviewed by Venier and Holmes 2010).
Early studies from Bent (1953) and MacArthur (1958) reported an average of 6 eggs laid
per nest, with a range of 4–9. This large variation in clutch size is hypothesized to result
from an adaptive response to budworm outbreaks (i.e. increased food supply), which
would allow for a rapid increase in population size (reviewed by Venier and Holmes
2010). Nest cups are made of sphagnum moss (Sphagnum sp.), spruce twigs and other
plant material, and are usually located at the top of conifers in thick foliage near the trunk
(ca. 10–18 m high; reviewed by Baltz and Latta 1998). There is no information available
on renesting events; however, this behaviour is common in other warbler species and is
likely to occur if the initial nesting attempt fails early in the breeding season (Morse and
Poole 2005, Porneluzi et al. 2011). Owing to the relative rarity of this species, the basic
details about its breeding biology (e.g., reproductive success) remain unknown and are
based mainly on studies from Ontario (Kendeigh 1947) and Maine (MacArthur 1958),
with limited sample sizes. No recent studies have contributed to our understanding of
population dynamics.
5
Figure 1. Black-throated green warbler distribution in Alberta.
6
Figure 2. Bay-breasted warbler distribution in Alberta.
7
Figure 3. Cape May warbler distribution in Alberta.
8
1.2 Population Trends
Data from the Breeding Bird Survey (BBS) suggest that nationally: the black-throated
green warbler declined by 1.2% annually from 1999–2009; the bay-breasted warbler
declined by 3% annually from 1970–2009; and the Cape May warbler declined by 5.3%
annually from 1999–2009 (Environment Canada 2012b). Data from the Lesser Slave
Lake Bird Observatory suggest substantially lower abundances of these three warbler
species compared to other more common boreal songbirds. See Appendix 1 for more
details about population trends.
1.3 Threats to Populations
The observed national decline is significantly correlated with decreasing spruce budworm
populations (Venier and Holmes 2010). Predators of nests, adults and fledglings are
poorly documented (Venier et al. 2011), but these three warbler species are likely
vulnerable to several predators that prey on songbirds breeding in similar habitat (e.g.,
mammals, raptors, and corvids; Bayne and Hobson 1997, Cotterill and Hannon 1999,
Ball et al. 2009). Although the specific causes of mortality of these three species are
unknown, it is safe to assume that they would be equally or more vulnerable to the
numerous sources of mortality reported to explain the overall continental decline in
songbirds (Stutchbury 2007). Human land use and infrastructure (Robinson and Wilcove
1994, Donovan and Flather 2002, Bayne et al. 2012), climate change (Butler 2000,
Wilson et al. 2011), bioaccumulation of pollutants (Fairbrother et al. 2004), species
invasion (Gurevitch and Padilla 2004, Loss et al. 2012) and infectious diseases (Dhondt
et al. 1998, LaDeau et al. 2007) are all also potential causes for the observed decline in
these three species.
Human activities often result in habitat loss, i.e. conversion of suitable habitat into
unsuitable habitat, and fragmentation, i.e. dissection of remaining habitat, which are
important causes of population declines in North American songbirds (e.g., Robbins et al.
1989, Böhning-Gaese et al. 1993, Robinson et al. 1995, Schmiegelow and Mönkkönen
2002). More moderate human activities that cause habitat alteration instead of loss can
still have significant effects on songbird populations — particularly those of late-
successional forest specialists — because the resulting habitat, while still usable, is often
of lower quality (Guénette and Villard 2005, Pérot and Villard 2009, Vanderwel et al.
2009). Habitat loss, alteration and fragmentation in Alberta’s forests are mainly caused
by forestry, agriculture, oil and gas activities, natural disturbances (insect outbreaks and
forest fires), and urban expansion. Human activities encountered by these three warbler
species at migratory stopovers and on their wintering grounds can also threaten
populations.
1.3.1. Forestry Sector
Current forestry practices are directed at maximizing the rate and volume of timber and
pulp harvested. Pressure from forestry operations in British Columbia and Alberta is
threatening the amount of suitable habitat remaining for these three warbler species,
particularly within the western extent of the bay-breasted warbler and Cape May
9
warbler’s ranges (reviewed by Cooper et al. 1997a,b; Norton 2001a,b). Older stands are
targeted first for harvest, which reduces the amount of old forest on the landscape. This,
coupled with a short rotation age (ca. 70 years), leads to a younger landscape overall
(Schneider et al. 2003). In Saskatchewan, the black-throated green warbler occurred more
frequently in stands of post-rotation age (100 –110 years after clearcuts; Cumming and
Diamond 2002). As well, silvicultural practices can lead to habitat alteration by the
“unmixing of the mixedwoods” (Hobson and Bayne 2000a), where the structure and
composition of diverse mixedwood stands are lost when stands are replanted with single
species post-harvest. These land practices result in an immediate and long-term reduction
of suitable warbler breeding habitat.
Although alternative harvesting techniques such as variable retention and aggregated
harvest are being explored, their potential to reduce warbler population declines in
Alberta is largely unknown. Studies of alternative harvesting techniques have shown that
there were significantly lower abundances of black-throated green warbler in harvested
stands than in control plots in Alberta (Norton and Hannon 1997) and elsewhere
(Flaspohler et al. 2002, Guénette and Villard 2005, Atwell et al. 2008, Millington et al.
2011, Kardynal et al. 2012).
Potvin and Bertrand (2004) suggested that mature forest patches of more than 50 ha are
required to maintain bay-breasted warbler populations. In Alberta and elsewhere, the
black-throated green warbler is generally absent from some small forest remnants (< 100
ha; Askins and Philbrick 1987, Hobson and Bayne 2000b, Hannah 2006). Significant
edge avoidance was also observed in the black-throated green warbler in Alberta (Villard
et al. 2007). Edge avoidance may also occur due to increased predation or microclimate
effects (Hagan et al. 1996, Flaspohler et al. 2001), and may lead to a reduction in the
functional area of the remaining patch (Villard 1998). In Alberta, neither nest predation
nor nest parasitism appears to have increased due to fragmentation from forestry
(Cotterill and Hannon 1999, Song and Hannon 1999). Predation pressure may become
more significant when landscape conversion reaches a threshold level, as in some
agricultural landscapes (Koper and Schmiegelow 2006).
Creation of roads as a result of forest management also dissects remaining stands and
increases edge habitat, which can have negative effects permeating into the forest interior
(Hobson and Bayne 2000b, Rempel 2007). Lower densities have also been reported near
roads (Merrill et al. 1998, Ortega and Capen 2002). In Ontario, the bay-breasted warbler
is associated with undisturbed areas and low edge density (< 18.5 m/ha; Rempel 2007,
see also Hobson and Bayne 2000b).
The landscape context surrounding forest remnants also needs to be taken into account, as
the degree of regional fragmentation can affect local bird abundance (Vernier et al. 2002,
Venier and Pearce 2007). Highly unsuitable habitat surrounding remnants may result in
songbirds being reluctant to cross gaps between patches of good habitat, thereby reducing
connectivity (Bélisle and Desrochers 2002, Brotons et al. 2003). Even large remnants
may be considered unsuitable habitat if they are isolated, or the composition of
surrounding habitat impedes movements (Bélisle and Desrochers 2002, Brotons et al
10
2003). In New Brunswick, habitat loss at local and landscape scales was associated with
lower apparent survival, explaining at least partially the reduced occurrence of black-
throated green warbler in these landscapes (Zitske et al. 2011). In Quebec, Drolet et al.
(1999) showed that the bay–breasted warbler was absent from landscapes with < 55%
forest cover.
Habitat corridors have been explored as a landscape feature that may mitigate the effects
of fragmentation, but their efficacy remains largely unknown (Hannon and Schmiegelow
2002). For example, in Quebec, the probability that the black-throated green warbler
crossed gaps decreased sharply with gaps larger than 25–40 m wide (Rail et al. 1997). In
New England, Meiklejohn and Hughes (1999) found lower abundances in buffer strips (<
100 m wide) than within reference sites (see also Freedman et al. 1981, Darveau et al.
1995, Hanowski et al. 2003). However, Darveau et al. (1995) suggest that 60-m wide
buffer strips could support forest-dwelling birds.
For successful management of these species in Alberta, habitat requirements at both the
stand and landscape scales need to be considered. Research projects in Alberta examining
songbird response to forestry have been unable to make conclusions regarding the effects
on these species, largely because of their low abundance. However, it is likely that
populations in Alberta respond similarly to habitat loss and alteration as do populations
elsewhere in the breeding range or other forest specialists for which empirical data are
available (Vanderwel et al. 2009).
1.3.2. Energy Sector
An increase in energy exploration and development in Alberta in recent years has
resulted in habitat loss, alteration, and fragmentation in late-successional forests, through
the creation of permanent structures (compressor stations, wellheads, in situ oil
extraction) and linear features (roads, seismic lines, pipelines; see Bayne et al. 2005,
Lankau et al. in review and references therein). Seismic line density can reach up to
10 km per km2 in some townships (Lee and Boutin 2006). Currently, regulations exist for
revegetating seismic lines, but specific guidelines are lacking. Additional negative effects
on songbirds resulting from oil and gas activities include reduced abundance and
breeding success in areas near chronic industrial noise such as compressor stations
(Habib et al. 2007, Bayne et al. 2008), and mortality caused by oil industry flare stacks
(Bjorge 1987).
1.3.3. Agriculture
One type of habitat loss occurs where mature forests are converted for agriculture at the
southern extent of the boreal forest (Hobson et al. 2002). Habitat fragmentation
associated with agricultural expansion may lead to an increase in the abundance of nest
parasites (i.e. brown-headed cowbird) and predators (Robinson et al. 1995, Bayne and
Hobson 1997). Parasitism by brown-headed cowbirds has been reported in black-throated
green warblers, but its effect on population dynamics remains unknown (Morse and
Poole 2005). Parasitism by brown-headed cowbirds has also been reported for the Cape
May warbler (Friedmann and Kiff 1985) and bay-breasted warbler (Sealy 1979), but may
be rare because there is little overlap between the ranges and preferred habitat types of
11
these species (Venier et al. 2011). Nonetheless, predation and parasitism rates are often
higher in forests fragmented by agricultural systems compared to those fragmented by
forest management (Bayne and Hobson 1997).
1.3.4. Natural Disturbances (insect outbreak and forest fire)
Fluctuations in spruce budworm outbreaks have been shown to regulate population
densities of bay-breasted and Cape May warblers (Patten and Burger 1998, Sleep et al.
2009, Venier and Holmes 2010); these species are considered to be spruce budworm
specialists (Venier et al. 2009, Venier and Holmes 2010). In Canada, the abundance of
spruce budworm in a given year is a good predictor of the population levels of these two
warblers in the following year (Sleep et al. 2009). The effects of spruce budworm
outbreaks on songbirds are usually positive, and no change in clutch size has been
reported in black-throated green warbler during outbreaks; however increasing
intraspecific competition from other songbirds could negatively influence the abundance
of this species (Patten and Burger 1998). Conversely, the modification of the stand
structure and composition following an infestation would support higher abundance of
black-throated green warbler (DesGranges and Rondeau 1995).
Currently, aerial spraying of biological insecticides is used in Alberta to control spruce
budworm outbreaks from epidemic to endemic levels (Alberta Sustainable Resource
Development 2002). Chemical insecticides for spruce budworm were replaced in Canada
in the early 1990s by bacterial insecticides that target the insect’s digestive system (van
Frankenhuyzen 1990). This greatly reduces the potential direct impacts on songbirds’
health (Pearce et al. 1976, Pearce and Garrity 1981, Venier et al. 2011). Spraying is
effective at maintaining spruce budworm population levels locally (S. Ranasinghe pers.
comm., cited by Norton 2001a), and might result in negative effects on spruce budworm
specialists. However, the abundance of bay-breasted warblers was higher in sites
protected from a budworm outbreak (controlled by insecticides) than those monitored 10
years post-outbreak (DesGranges and Rondeau 1995; see also Venier and Holmes 2010).
Venier et al. (2011) also suggest that spraying is an unlikely cause for the overall
decrease in population levels of bay-breasted warblers because it takes place over a small
proportion of the species’ breeding range. A similar response can be expected for the
Cape May warbler (Norton 2001b). The effects of spruce budworm control on the
population dynamics of black-throated green warblers breeding in Alberta remain
unknown.
Forest fire is an important component of stand dynamics in the boreal forest and occurs
over a large spatial extent. For example, from 2002–2011, the annual average area burned
in Alberta was 220 875 ha, while the annual mean number of wildfires was 1541 (Alberta
Environment and Sustainable Resource Development 2012b). Wildfires result in habitat
loss for late-successional forest specialists, but the duration of this negative effect is
unknown. Hence, the response of these warblers to forest fire remains unknown in the
province, but a study in Northern Minnesota showed that the bay-breasted warbler was
common in a jack-pine–black-spruce forest prior to a fire and was seen only sporadically
even 30 years after the fire occurred (Haney et al. 2008). Also in Minnesota, Shulte and
Niemi (1998) showed that bay-breasted warbler was more abundant in harvested areas
12
(clearcuts with patches of residual trees) than in burned stands (years 2 and 3 post-fire).
Yet, in northern Georgia, the species had similar densities among controls and burns of
different severities and showed no relationships with time since fire during the first six
years post-fire (Rush et al. 2012).
1.3.5. Urban Expansion
According to Alberta Treasury Board and Finance (2012), under a scenario of medium
growth rate, the population is expected to increase by over 2 million people and reach
about 6 million by 2041. In Ontario, the black-throated green warbler shows lower
abundance in developed (housing/cottage) versus undeveloped areas (Ford and
Flaspohler 2010). Recent studies suggest that millions of birds die annually from
collisions with houses and other buildings (Bayne et al. 2012, Machtans et al. 2013).
Furthermore, between 100 and 350 million birds are preyed upon annually by cats in
Canada (Blancher 2013). Although these numbers might reflect a low proportion of all
birds breeding in Canada, this source of mortality can have disproportionately negative
effects on species with low population sizes, especially when considering the cumulative
effects of all other sources of human land use.
1.3.6. Winter and Migration Stopover Habitat
All the threats listed above also apply to winter and migration stopover habitat (Mehlman
et al. 2004, reviewed by Stutchbury 2007). Rappole and McDonald (1994) suggest that
habitat degradation on the wintering grounds may be a key factor underlying observed
declines of migratory songbirds (see also Faaborg et al. 2010). Recent studies have
determined that lower-quality winter habitat can influence reproductive output during the
breeding season through carry-over effects (Norris et al. 2004, Holmes 2007), and have
highlighted the importance of understanding species’ status throughout their annual cycle
(Sillett and Holmes 2002, Greenberg and Marra 2005).
The population of black-throated green warblers in Saskatchewan declined from 1972 to
1992, and events on the wintering grounds have been suggested as a potential factor
underlying this pattern (Kirk et al. 1997). Very little information is available on the
ecology of black-throated green warblers during migration, but migratory stopover sites
are often located in areas with high human densities, and many have been lost or altered
because of development (Morse and Poole 2005). However, this species may be less
threatened by tropical deforestation than other neotropical migrants, as it occupies a large
wintering range and uses a broad range of habitats (Morton 1992).
While bay-breasted warblers are found in both primary and second-growth forests during
migration and the non-breeding season, their geographic distribution on the wintering
grounds is quite limited (reviewed by Venier et al. 2011). This may lead to higher
conservation priorities if population levels continue to decline.
13
2.0 GOALS AND OBJECTIVES
2.1 Goal
Maintain breeding populations of black-throated green warblers, bay-breasted warblers
and Cape May warblers throughout their historical range in Alberta.
2.2 Objectives
1. Inventory, monitoring and assessment: Continue monitoring boreal bird populations
in Alberta to understand population sizes, distributions and trends, and habitat
requirements of these warbler species.
2. Habitat conservation and management: Implement appropriate habitat conservation
and management practices.
3. Research: Address the important gaps in our knowledge of the population dynamics
of these warbler species in Alberta.
4. Education and communication: Improve education of and communication with
government, industry, public and landowners about the importance of habitat
conservation and neotropical migrants.
3.0 MANAGEMENT ACTIONS
3.1 Monitoring and Assessment
Community-level surveys such as line transects and point counts are important tools for
documenting presence/absence, relative abundance, and coarse-scale habitat associations
of bird species. These surveys can be more easily applied over larger spatial scales than
can more intensive local demographic studies. However, demographic studies using
techniques such as spot-mapping and mark-recapture are critical to understanding
population dynamics and growth rates. They would provide information about the
mechanisms underlying the status of these three warbler species in Alberta. The bay-
breasted and Cape May warblers can be difficult to detect during surveys because their
song is high, thin and quiet. Thus, care should be taken when training observers and
planning sampling efforts. Sampling methods and protocols should also be standardized
to simplify comparisons between studies (e.g., meta-analyses) and trend analyses. Trend
analyses should be conducted every five years to implement proactive adaptive
management and conservation actions (Wilhere 2002, Norton 2005, McDonald-Madden
et al. 2010).
There are currently several projects monitoring these warbler populations in Alberta.
These projects are being conducted by universities and colleges, consulting firms,
industry, and both government and non-governmental organizations. Continued long-
14
term monitoring is critical to detect changes in population size, distribution and trend,
and habitat associations. Below are some examples of monitoring programs taking place
in the province:
• Alberta Biodiversity Monitoring Institute
o Established in 2003, this initiative includes broad-scale surveys
throughout Alberta, including remote areas of the province (Alberta
Biodiversity Monitoring Institute 2012; see also Stadt et al. 2006, Nielsen
et al. 2009).
• Alberta Breeding Bird Atlas
o This volunteer-based monitoring initiative aids in identifying the
distribution and abundance of Alberta birds (Federation of Alberta
Naturalists 2007).
• Breeding Bird Survey
o Broad-scale, long-term roadside surveys are used to monitor the status and
trends of North American bird populations (Sauer et al. 2007).
• Calling Lake Fragmentation Project
o Ongoing since 1993, this intensive landscape experiment explores the
effect of forest fragmentation due to harvesting on the songbird
community (principal investigators: Dr. E. M. Bayne and Dr. F. K. A.
Schmiegelow).
• Ecosystem Management by Emulating Natural Disturbance (EMEND)
o This long-term project examines the effects of variable retention after
harvest and forest regeneration on ecosystem integrity (project leaders: Dr.
J. R. Spence and Dr. J. Volney).
• Alberta Migration Monitoring stations (Lesser Slave Lake Bird Observatory,
Beaverhill Bird Observatory, Inglewood Bird Sanctuary, and Owl Moon
Environmental Inc. in the Fort McMurray region)
o These stations use banding and the MAPS program (Monitoring Avian
Productivity and Survival) to collect information on changes in bird
populations, including abundance, sex and age ratios, and routes and
timing of migration.
• Integrated Monitoring Plan for the Oil Sands: terrestrial biodiversity component
(Canadian Wildlife Service):
o The collection of point count data is used to monitor habitat disturbances
by oil sands development and to improve bird-habitat density models.
Communication and collaboration between stakeholders and researchers are required to
achieve a more complete understanding of the status these three warblers and the effects
15
of conservation actions. Examples of such work are currently conducted by the Boreal
Avian Modelling Project (http://www.borealbirds.ca/), Ebird
(http://ebird.org/content/ebird), and Boreal Songbird Initiative
(http://www.borealbirds.org/index.shtml). All data should be stored in the Fisheries and
Wildlife Management Information System (FWMIS) — a standardized data collection,
storage and retrieval system for both government and the public (Alberta Environment
and Sustainable Resource Development 2012c).
3.2 Habitat Conservation and Management
In Alberta, these warbler species breed exclusively in the Boreal Forest and Foothills
natural regions. Black-throated green warblers breed exclusively in spruce forests,
mixedwood stands dominated by large spruce, and deciduous-dominated mixedwood
stands. For bay-breasted and Cape May warblers, higher densities are reached in mature
and old coniferous forests, and all three species show a strong association with mature
and interior forests (Boreal Avian Modelling project 2012a,b,c). The recommendations
for stand and landscape management apply to all these habitats types.
Implementation of these recommendations could be assisted by modelling the amount of
habitat available given alternative scenarios of human land use (e.g., ALCES -
www.alces.ca) or by using spatially explicit approaches to optimize the amount of habitat
protected given different predicted economic opportunities (e.g., Marxan; Game and
Grantham 2008).
The following recommendations should be considered when developing both landscape-
level plans (such as forest management plans, land-use framework regional plans, etc.) as
well as operational policies and plans (such as wildlife standards and guidelines, forestry
operational ground rules, etc.).
Stand-Level Management
• Forest Age
o Blocks of old forest (stands > 100 years old) should be maintained on the
landscape to support high densities (Boreal Avian Modelling Project
2012a,b,c) and for the persistence of late-successional forest specialists.
• Forest Composition
o Conservation efforts should ensure that white spruce and balsam fir are
maintained in coniferous and mixedwood stands and that reforestation
corresponds to pre-harvest conditions or mimics natural disturbance regimes
(Robichaud and Villard 1999).
o Large diameter trees are key habitat features for these species (especially
black-throated green warbler: > 50 cm dbh for white spruce and > 20 cm dbh
for paper birch) and they should be maintained to provide required local
conditions.
16
• Forest Configuration
o Remnant forest blocks should be larger than 50 ha (Potvin and Bertrand
2004). Note that other songbirds with similar territory size have been shown
to be absent from forest blocks < 100 ha (Hannah 2006). However,
maintaining breeding populations might require substantially larger blocks of
forest than what is needed to maintain the probability of presence of a species
(e.g., Poulin et al. 2008).
o Because of negative edge effects, edge density and the edge-to-area ratio of
remnant patches should be minimized (< 18.5 m/ha; Rempel 2007). Creation
of linear features (i.e. roads, cutlines and pipelines) should be minimized in
areas with large patches of high-quality breeding habitat.
Landscape-Level Management
o The bulk of industrial activities should be conducted during the non-breeding
season (1 August–30 April) to prevent the destruction or disturbance of birds
and their nests (see Migratory Birds Convention Act).
o The boreal landscape needs to be managed at a broad spatial scale with
consideration of cumulative effects of all human land use (Schneider et al.
2003, 2011; Aumann et al. 2007).
o Human activities should be modified to mimic natural disturbances over large
forest landscapes (e.g., use aggregated harvest blocks to emulate fire regimes;
Carlson and Kurz 2007). Elaboration of specific mitigation programs is also
imperative to minimize the lifespan of industrial footprints (MacDonald et al.
2012).
o The amount, composition, and distribution of late-successional stands should
be monitored to ensure that they are present in adequate proportions on the
landscape and meet conservation targets. Rompré et al. (2010) suggest that
most sensitive forest species could be maintained with at least 40% of residual
forest maintained on the landscape, but Drolet et al. (1999) showed that more
than 55% of residual forest is required for maintaining the bay-breasted
warbler.
o Contiguous areas of boreal forest (e.g., reserve networks) should be protected
from human development to serve as refugia and ensure the existence of
source populations (population growth rate > 1), which could be used as
ecological benchmarks.
o Alberta’s landscapes are subject to intensive human activities, and static
reserves may not ensure a continuing presence of suitable habitat (Leroux et
17
al. 2007). Hence, implementing dynamic reserve design may be worth
exploring.
o Consideration should be given to the use of multi-species or umbrella species
models to achieve landscape targets for these warblers because it is not
feasible to set habitat targets for all individual species when developing plans.
3.3 Research
To implement efficient adaptive management strategies, efforts should address the
following gaps in our knowledge of the ecology, particularly breeding biology, of these
three warblers in Alberta:
• Determine habitat-specific breeding success, productivity (e.g., number of young
produced per unit area), and other vital rates such as survival, dispersal and
recruitment, by using a combination of mark-recapture studies and genetic/stable
isotopes analyses.
• Very little information exists on bay-breasted and Cape May warbler density and
reproductive success within areas of spruce budworm outbreaks in the province.
The short- and long-term implications of aerial spraying should be investigated.
• Provincial and species-specific estimates of mortality owing to collisions with
houses and buildings should be generated while accounting for expected
population growth rate of Albertans.
• Information collected through these first three actions should be used to generate
demographic models providing habitat-specific population growth rates.
• Determine the mechanisms underlying habitat-specific variation in population
growth rate (availability of resources, abundance of nest predators, human
disturbance, etc.).
• Determine the patch size and landscape configuration that supports the highest
densities of the three species and the most productive individuals.
• Use all of the above information to model the future status of these species, based
on alternative scenarios of human land use, to inform stakeholders and determine
the most efficient management strategies.
• Evaluate the potential of modelling the response of an umbrella species (i.e., a
‘‘species that requires large areas of suitable habitat to maintain viable
populations and whose requirements for persistence are believed to encapsulate
those of an array of associated species’’; Carignan and Villard 2002) to
determining simultaneously how populations of these warblers and other species
with similar habitat requirements respond to human land use.
3.4 Education and Communication
Although the song of the black-throated green warbler is unique, it often forages high in
mature trees and may not be recognized by untrained observers. Similarly, bay breasted
and Cape May warblers forage high in trees, and their songs can easily be confused with
other songbird species breeding in similar habitat. Brochures (or other outreach materials)
18
would be an important tool for describing these species and their habitat needs, as well as
communicating the conservation needs of these warblers and other bird species facing
similar threats. It is essential to maintain communication with government, public,
industry and landowners regarding breeding habitat description, timing of breeding, and
why these species are sensitive to human disturbance. Also important is to emphasize the
benefits of maintaining large tracts of old forest for a variety of resident and migratory
species inhabiting the boreal forest. Such information could be communicated by
interpretive programs and visitor centres of provincial and federal parks, presentations to
schools and recreational clubs, and in the media. Monitoring the effectiveness of these
programs is critical to maximize their efficiency.
4.0 SUMMARY
The black-throated green warbler is considered a mature and interior forest species, and
the bay-breasted and Cape May warblers are considered late-successional forest
specialists. All three species face multiple threats resulting from industrial activities —
the amount of habitat lost, altered and fragmented by such activities is cause for concern
regarding the viability of many wildlife species in Alberta. Long-term community-level
surveys as well as detailed demographic studies are needed to adequately monitor these
three warbler species and to determine the amount and spatial configuration of the
optimal habitat required for maintaining source populations. Integration of the listed
recommendations into current land management practices would help protect habitat and
favour conservation of these songbirds.
Particularly important to ensure population persistence of these warblers in Alberta is to
maintain old coniferous stands and old mixedwood forests with an overstory that
comprises large white spruce and paper birch. These stand types should be maintained in
large blocks with minimal edge. Control of spruce budworms should be applied with
caution, as bay-breasted and Cape May warblers are considered spruce budworm
specialists and their population levels are correlated with the abundance of this prey. A
key step in effectively managing black-throated green warbler populations is the
collaboration of the different stakeholders in sharing of knowledge and minimizing
cumulative effects on the landscape.
This conservation management plan should be considered a “living document”, and any
new and relevant information should be incorporated when available. A complete review
of this plan should take place every five years to include new population and habitat data
and adjust the conservation recommendations accordingly. The review should be led by
Alberta Fish and Wildlife Division, in consultation with boreal songbird experts and
other stakeholders.
19
5.0 LITERATURE CITED
Alberta Biodiversity Monitoring Institute. 2012. Biodiversity Browser. Edmonton, CA.
Online: http://www.abmi.ca/abmi/biodiversitybrowser/species.jsp. Accessed
28/10/2012.
Alberta Environment and Sustainable Resource Development. 2012a. General Status of
Alberta Wild Species 2010. Government of Alberta, Alberta, CA. Online:
http://esrd.alberta.ca/fish-wildlife/species-at-risk/wild-species-status-search.aspx
Alberta Environment and Sustainable Resource Development. 2012b. Historical wildfire
information. Government of Alberta, Alberta, CA. Online:
http://www.srd.alberta.ca/Wildfire/WildfireStatus/HistoricalWildfireInformation/
Default.aspx.
Alberta Environment and Sustainable Resource Development. 2012c. FWMIS.
Government of Alberta, Alberta, CA. Online:
http://www.srd.alberta.ca/FishWildlife/FWMIS/Default.aspx. Accessed
28/10/2012.
Alberta Sustainable Resource Development. 2002. Integrated spruce budworm
management strategy. Government of Alberta, Alberta, CA.
Alberta Treasury Board and Finance. 2012. Alberta population projection 2012–2041.
2012. Government of Alberta, Alberta, CA.
Askins, R. A., and M. J. Philbrick. 1987. Effect of changes in regional forest abundance
on the decline and recovery of a forest bird community. Wilson Bulletin 99:7–21.
Atwell, R. C., L. A. Schulte and B. J. Palik. 2008. Songbird response to experimental
retention harvesting in red pine (Pinus resinosa) forests. Forest Ecology and
Management 255:3621–3631.
Aumann, C., D. R. Farr and S. Boutin. 2007. Multiple use, overlapping tenures, and the
challenge of sustainable forestry in Alberta. Forestry Chronicle 83:642–650.
Ball, J., E. M. Bayne and C. S. Machtans. 2009. Video identification of boreal forest
songbird nest predators and discordance with artificial nest studies. Proceedings
of the fourth International Partners in Flight Conference: Tundra to Tropics: 37–
44.
Baltz, M. E., and S. C. Latta. 1998. Cape May Warbler (Setophaga tigrina). In Poole, A.,
editor. The Birds of North America. Cornell Lab of Ornithology. Online:
http://bna.birds.cornell.edu/bna/species/332.
Bayne, E. M., and K. A. Hobson. 1997. Comparing the effects of landscape
fragmentation by forestry and agriculture on predation on artificial nests.
Conservation Biology 11:1418–1429.
20
Bayne, E. M., S. L. Van Wilgenburg, S. Boutin and K. A. Hobson. 2005. Modeling and
field-testing of ovenbird (Seiurus aurocapillus) responses to boreal forest
dissection by energy sector development at multiple spatial scales. Landscape
Ecology 20:203–216.
Bayne, E. M., L. Habib and S. Boutin. 2008. Impacts of chronic anthropogenic noise
from energy-sector activity on abundance of songbirds in the boreal forest.
Conservation Biology 22(5):1186–1193.
Bayne, E. M., C. A. Scobie and M. Rawson-Clark. 2012. Factors influencing the annual
risk of bird-window collisions at residential structures in Alberta, Canada.
Wildlife Research 39:583–592.
Bélisle, M., and A. Desrochers. 2002. Gap-crossing decisions by forest birds: an
empirical basis for parameterizing spatially-explicit, individual-based models.
Landscape Ecology 17:219–231.
Bent, A. C. 1953. Life histories of North American wood warblers. U.S. National
Museum Bulletin 203.
Bjorge, R. R. 1987. Bird kill at an oil industry flare stack in northwest Alberta. Canadian
Field-Naturalist 101:346–350.
Blancher, P. 2013. Estimated number of birds killed by house cats (Felis catus) in
Canada. Avian Conservation and Ecology 8(2): 3. Online: http://www.ace-
eco.org/vol8/iss2/art3/.
Böhning-Gaese, K., M. L. Taper and J. H. Brown. 1993. Are declines in North American
insectivorous songbirds due to causes on the breeding range? Conservation
Biology 7:76–86.
Boreal Avian Modelling Project. 2012a. Black-throated green warbler. Edmonton, CA.
Online: http://www.borealbirds.ca/avian_db/accounts.php/Setophaga+virens.
Accessed 15/12/2012.
Boreal Avian Modelling Project. 2012b. Bay-breasted warbler. Edmonton, CA. Online:
http://www.borealbirds.ca/avian_db/accounts.php/Setophaga+castanea. Accessed
28/10/2012.
Boreal Avian Modelling Project. 2012c. Cape May warbler. Edmonton, CA. Online:
http://www.borealbirds.ca/avian_db/accounts.php/Setophaga+tigrina. Accessed
15/12/2012.
Brotons, L., M. Mönkkönen and J. L. Martin. 2003. Are fragments islands? Landscape
context and density-area relationships in boreal forest birds. American Naturalist
162:343–357.
21
Butler, R. W. 2000. Stormy seas for some North American songbirds: are declines related
to severe storms during migration. Auk 117:518–522.
Carignan, V., and M.-A. Villard. 2002. Selecting indicator species to monitor ecological
integrity: a review. Environmental Monitoring and Assessment 78:45–61.
Carlson, M., and W. A. Kurz. 2007. Approximating natural landscape pattern using
aggregated harvest. Canadian Journal of Forest Research 37:1846–1853.
Cooper, J. M., K. A. Enns and M. G. Shepard. 1997a. Status of the bay-breasted warbler
in British Columbia. British Columbia Ministry of the Environment, Lands and
Parks, Wildlife Working Report No. WR-79, British Columbia, CA.
Cooper, J. M., K. A. Enns and M. G. Shepard. 1997b. Status of the Cape May warbler in
British Columbia. British Columbia Ministry of the Environment, Lands and
Parks, Wildlife Working Report No. WR-82, British Columbia, CA.
Cotterill, S. E., and S. J. Hannon. 1999. No evidence of short-term effects of clear-cutting
on artificial nest predation in boreal mixedwood forests. Canadian Journal of
Forest Research 29:1900–1910.
Crawford, H. S., and D. T. Jennings. 1989. Predation by birds on spruce budworm
Choristoneura fumiferana: functional numerical and total responses. Ecology
70:152–163.
Cumming, E. E. 2004. Habitat segregation among songbirds in old-growth mixedwood
forest. Canadian Field-Naturalist 118:45–55.
Cumming, E. E., and A. W. Diamond. 2002. Songbird community composition versus
forest rotation age in Saskatchewan boreal mixedwood forest. Canadian Field-
Naturalist 116:69–75.
Darveau, M., P. Beauchesne, L. Bélanger, J. Huot and P. Larue. 1995. Riparian forest
strips as habitat for breeding birds in boreal forest. Journal of Wildlife
Management 59:67–78.
DesGranges, J. L., and G. Rondeau. 1995. Modifications des communautés d’oiseaux de
la sapinière suite au ravage d’une épidémie d’insectes. Forestry Chronicle
71:201–210.
Donovan, T. M., and C. H. Flather. 2002. Relationships among North American songbird
trends, habitat fragmentation, and landscape occupancy. Ecological Applications
12:364–374.
Dhondt, A. A., D. L. Tessaglia and R. L. Slothower. 1998. Epidemic mycoplasmal
conjunctivitis in house finches from eastern North America. Journal of Wildlife
Diseases 34:265–280.
22
Drolet, B, A. Desrochers and M.-J. Fortin. 1999. Effects of landscape structure on nesting
songbird distribution in a harvested boreal forest. Condor 101:699–704.
Endangered Species Conservation Committee. 2001. Black-throated Green Warbler
Initial Conservation Action Statement. Recommended to the Minister of
Sustainable Resource Development. Government of Alberta, Alberta, CA.
Endangered Species Conservation Committee. 2002a. Bay-breasted Warbler Initial
Conservation Action Statement. Recommended to the Minister of Sustainable
Resource Development. Government of Alberta. Alberta, CA.
Endangered Species Conservation Committee. 2002b. Cape May Warbler Initial
Conservation Action Statement. Recommended to the Minister of Sustainable
Resource Development. Government of Alberta, Alberta, CA.
Environment Canada. 2012a. Status of Birds in Canada – 2010. Government of Canada,
Ontario, CA. Online: http://www.ec.gc.ca/soc-sbc/index-
eng.aspx?sL=e&sY=2010. Accessed 28/10/2012.
Environment Canada. 2012b. Breeding bird survey – Canadian results. Government of
Canada, Ontario CA. Online: http://ec.gc.ca/reom-
mbs/default.asp?lang=En&n=0D74F35F-1. Accessed 28/10/2012.
Faaborg J., R. T. Holmes, A. D. Anders, K. L. Bildstein, K. M. Dugger, S. A. Gauthreaux
Jr., P. Heglund, K. A. Hobson, A. E. Jahn, D. H. Johnson, S. C. Latta, D. J.
Levey, P. P. Marra, C. L. Merkord, E. Nol, S. I. Rothstein, T. W. Sherry, T. S.
Sillett, F. R. Thompson III and N. Warnock. 2010. Conserving migratory land
birds in the new world: do we know enough? Ecological Applications 20:398–
418.
Fairbrother A., J. Smits and K.A. Grasman. 2004. Avian immunotoxicology. Journal of
Toxicology and Environmental Health, Part B: Critical Reviews 7:105–137.
Federation of Alberta Naturalists. 2007. The atlas of breeding birds of Alberta: a second
look. Federation of Alberta Naturalists. Alberta, CA.
Flaspohler, D. J., S. A. Temple and R. N. Rosenfield. 2001. Species-specific edge effects
on nest success and breeding bird density in a forested landscape. Ecological
Applications 11:32–46.
Flaspohler, D. J., C. J. Fisher Huckins, B. R. Bub and P. J. Van Dusen. 2002. Temporal
patterns on aquatic and avian communities following selective logging in the
upper great lakes region. Forest Science. 48:339–349.
Ford, M. T., and D. J. Flaspohler. 2010. Scale-dependent response by breeding songbirds
to residential development along Lake Superior. Wilson Journal of Ornithology
122:296–306.
23
Freedman, B., C. Beauchamp, I. A. McLaren and S. I. Tingley. 1981. Forestry
management practices and populations of breeding birds in Nova Scotia.
Canadian Field-Naturalist 95:307–311.
Friedmann, H., and L. F. Kiff. 1985. The parasitic cowbirds and their hosts. Proceedings
of the Western Foundation of Vertebrate Zoology 2:226–302.
Game, E. T., and H. S. Grantham. 2008. Marxan user manual. For Marxan version 1.8.10.
University of Queensland, Queensland, AUS, and Pacific Marine Analysis and
Research Association, British Columbia, CA.
Greenberg, R., and P. P. Marra. 2005. Birds of two worlds: the ecology and evolution of
migration. Johns Hopkins University Press. Maryland, USA.
Guénette, J.-S., and M.-A. Villard. 2005. Thresholds in forest bird response to habitat
alteration as quantitative targets for conservation. Conservation Biology 19:1168–
1180.
Gurevitch, J., and D. K. Padilla. 2004. Are invasive species a major cause of extinctions?
Trends in Ecology and Evolution 19:470–474.
Habib L., E. M. Bayne and S. Boutin. 2007. Chronic industrial noise affects pairing
success and age structure of ovenbirds (Seiurus aurocapilla). Journal of Applied
Ecology 44:176–184.
Hagan, J. M., W. M. Vander Haegen and P. S. McKinley. 1996. The early development
of forest fragmentation effects on birds. Conservation Biology 10:188–202.
Haney, A., S. Apfelbaum and J. M. Burris. 2008. Thirty years of post-fire succession in a
southern boreal bird community. American Midland Naturalist 159:421–433.
Hannah, T. A. 2006. Declines in the black-throated green warbler (Dendroica virens):
from pattern to process. M.Sc. Thesis. University of Alberta, Edmonton, CA.
Hannon, S. J., and F. K. A. Schmiegelow. 2002. Corridors may not improve the
conservation value of small reserves for most boreal birds. Ecological
Applications 12:1457–1468.
Hanowski, J., N. Danz, J. Lind and G. Niemi. 2003. Breeding bird response to riparian
forest harvest and harvest equipment. Forest Ecology and Management 174:315–
328.
Hobson, K. A., and E. M. Bayne. 2000a. Breeding bird communities in boreal forest of
western Canada: consequences of “unmixing” the mixedwoods. Condor 102:759–
769.
24
Hobson, K. A., and E. M. Bayne. 2000b. Effects of forest fragmentation by agriculture on
avian communities in the southern boreal mixedwoods of western Canada. Wilson
Bulletin 112:373–387.
Hobson K. A., E. M. Bayne and S. L. Van Wilgenburg. 2002. Large-scale conversion of
forest to agriculture in the boreal plains of Saskatchewan. Conservation Biology
16:1530–1541.
Holmes, R. T. 2007. Understanding population change in migratory songbirds: long-term
and experimental studies of Neotropical migrants in breeding and wintering areas.
Ibis 149 S2:2–13.
IUCN. 2013. The IUCN Red List of Threatened Species. Version 2013.2. Online:
http://www.iucnredlist.org/.
Kardynal, K. J., J. L. Morissette, S. L. Van Wilgenburg, E. M. Bayne and K. A. Hobson.
2012. Avian responses to experimental harvest in southern boreal mixedwood
shoreline forests: implications for riparian buffer management. Canadian Journal
of Forest Research 41:2375–2388.
Kendeigh, S. C. 1947. Bird population studies in the coniferous forest biome during a
spruce budworm outbreak. Ontario Department of Lands and Forests, Biological
Bulletin. Government of Ontario, Ontario, CA.
Kirk, D. A., and K. A. Hobson. 2001. Bird-habitat relationships in jack pine boreal
forests. Forest Ecology and Management 147:217–243.
Kirk, D. A., A. W. Diamond, K. A. Hobson and A. R. Smith. 1996. Breeding bird
communities of the western and northern Canadian boreal forest: relationship to
forest type. Canadian Journal of Zoology 74:1749–1770.
Kirk, D. A., A. W. Diamond, A. R. Smith, G. E. Holland and P. Chytyk. 1997.
Population changes in boreal forest birds in Saskatchewan and Manitoba. Wilson
Bulletin 109:1–27.
Kirk, D. A., D. A. Welsh, J. A. Baker, I. D. Thompson and M. Csizy. 2012. Avian
assemblages differ between old-growth and mature white pine forests of Ontario,
Canada: A role for supercanopy trees? Avian Conservation and Ecology 7:4.
Koper, N., and F. K. A. Schmiegelow. 2006. A multi-scaled analysis of avian response to
habitat amount and fragmentation in the Canadian dry mixed-grass prairie.
Landscape Ecology 21:1045–1059.
LaDeau, S., A. M. Kilpatrick and P. P. Marra. 2007. West Nile virus emergence and
large-scale declines of North American bird populations. Nature 447:710–714.
25
Lee, P., and S. Boutin. 2006. Persistence and development transition of wide seismic
lines in the western boreal plains of Canada. Journal of Environmental
Management 78:240–250.
Leroux, S. J., F. K. A. Schmiegelow, S. G. Cumming, R. B. Lessard and J. Nagy. 2007.
Accounting for system dynamics in reserve design. Ecological Applications
17:1954–1966.
Loss, S. R., G. J. Niemi and R. B. Blair. 2012. Invasions of non-native earthworms
related to population declines of ground-nesting songbirds across a regional extent
in northern hardwood forests of North America. Landscape Ecology 27:683–696
MacArthur, R. H. 1958. Population ecology of some warblers of Northeastern coniferous
forests. Ecology 39:599–619.
MacDonald, E., S. Quideau and S. Landhäusser. 2012. Rebuilding boreal forest
ecosystems after industrial disturbance. In Vitt, D., and J. Bhatti, editors.
Restoration and reclamation of boreal ecosystems. Cambridge University Press,
Cambridge, UK.
Machtans, C. S., C. H. R. Wedeles, and E. M. Bayne. 2013. A first estimate for Canada of the
number of birds killed by colliding with building windows. Avian Conservation and Ecology
8(1): ZZ. Online: http://dx.doi.org/10.5751/ACE-0568-0801ZZ.
McDonald-Madden, E., W. J. J. Probert, C. E. Hauser, M. C. Runge, H. P. Possingham,
M. E. Jones, J. L. Moore, T. M. Rout, P. A. Vesk and B. A. Wintle. 2010. Active
adaptive conservation of threatened species in the face of uncertainty. Ecological
Applications 20:1476–1489.
Mehlman D. W., S. E. Mabey, D. N. Ewert, C. Duncan, B. Abel, D. Cimprich, R. D.
Sutter and M. Woodrey. 2004. Conserving stopover sites for forest-dwelling
migratory landbirds. Auk 122:1281–1290.
Meiklejohn, B. A., and J. W. Hughes. 1999. Bird communities in riparian buffer strips of
industrial forests. American Midland Naturalist 141:175–184.
Merrill, S. B., F. J. Cuthbert and G. Oehlert. 1998. Residual patches and their
contribution to forest-bird diversity on northern Minnesota aspen clearcuts.
Conservation Biology 12:190–199.
Millington, J. D. A., M. B. Walters, M. S. Matonis, E. J. Laurent, K. R. Hall and J. Liu.
2011. Combined long-term effects of variable tree regeneration and timber
management on forest songbirds and timber production. Forest Ecology and
Management 262:718–729.
Morse, D. H. 1976. Variables determining the density and territory site of breeding
spruce-woods warblers. Ecology 57:290–301.
26
Morse, D. H., and A. F. Poole. 2005. Black-throated Green Warbler (Setophaga virens).
In Poole, A., editor. Birds of North America. Cornell Lab of Ornithology. Online:
http://bna.birds.cornell.edu/bna/species/055.
Morton, E. S. 1992. What do we know about the future of migrant landbirds? Pp. 579–
589 In Hagan, J. M. III, and D. W. Johnston, editors. Ecology and conservation of
neotropical migrant landbirds. Smithsonian Institute Press, Washington, DC.
NatureServe 2012. NatureServe Explorer. Virginia, USA. Online:
http://www.natureserve.org/explorer/. Accessed 28/10/2012.
Nielsen, S. E., D. L. Haughland, E. Bayne and J. Schieck. 2009. Capacity of large-scale,
long-term biodiversity monitoring programmes to detect trends in species
prevalence. Biodiversity and Conservation 18:2961–2978.
Norris, D. R., P. P. Marra, T. K. Kyser, T. W. Sherry and L.M. Ratcliffe. 2004. Tropical
winter habitat limits reproductive success on the temperate breeding grounds in a
migratory bird. Proceedings of the Royal Society of London Series B 271:59–64.
Norton, B. G. 2005. Sustainability: a philosophy of adaptive ecosystem management.
University of Chicago Press, Illinois, USA.
Norton, M. R. 1999. Status of the black-throated green warbler (Dendroica virens) in
Alberta. Alberta Environment, Fisheries and Wildlife Management Division, and
Alberta Conservation Association, Wildlife Status Report No. 23. Alberta, CA.
Norton, M. R. 2001a. Status of the bay-breasted warbler (Dendroica castanea) in
Alberta. Alberta Environment, Fisheries and Wildlife Management Division, and
Alberta Conservation Association, Wildlife Status Report No. 32. Alberta, CA.
Norton, M. R. 2001b. Status of the Cape May warbler (Dendroica tigrina) in Alberta.
Alberta Environment, Fisheries and Wildlife Management Division, and Alberta
Conservation Association, Wildlife Status Report No. 33. Alberta, CA.
Norton, M. R., and S. J. Hannon. 1997. Songbird response to partial-cut logging in the
boreal mixedwood forest of Alberta. Canadian Journal of Forest Research 27:44–
53.
Ortega, Y. K., and D. E. Capen. 2002. Roads as edges: effects on birds in forested
landscapes. Forest Science 48:381–390.
Patten, M. A., and J. C. Burger. 1998. Spruce budworm outbreaks and the incidence of
vagrancy in eastern North American wood-warblers. Canadian Journal of Zoology
76:433–439.
Pearce, P. A., and N. R. Garrity. 1981. Impact of aminocarb (Matacil) spraying on forest
songbirds in northern New Brunswick. Canadian Wildlife Service, Progress Note
121. Government of Canada, Ontario, CA.
27
Pearce, P. A., D. B. Peakall and A. J. Erskine. 1976. Impact on forest birds of the 1975
spruce budworm spray operation in New Brunswick. Canadian Wildlife Service,
Progress Note 62. Government of Canada, Ontario, CA.
Pérot, A., and M.-A. Villard. 2009. Putting density back into the habitat-quality equation:
case study of an open-nesting forest bird. Conservation Biology 23:1550–1557.
Porneluzi, P., M. A. Van Horn and T. M. Donovan. 2011. Ovenbird (Seiurus
aurocapilla). In Poole, A., editor. The Birds of North America. Cornell Lab of
Ornithology. Online: http://bna.birds.cornell.edu/bna/species/088.
Potvin, F., and N. Bertrand. 2004. Leaving forest strips in large clearcut landscapes of
boreal forest: a management scenario suitable for wildlife? Forestry Chronicle
80:44–53.
Poulin, J.-F., M.-A. Villard, M. Edman, P. J. Goulet and A.-M. Eriksson. 2008.
Thresholds in nesting habitat requirements of an old forest specialist, the brown
creeper (Certhia americana), as conservation targets. Biological Conservation
141:1129–1137.
Rail, J.-F., M. Darveau, A. Desrochers and J. Huot. 1997. Territorial responses of boreal
birds to habitat gaps. Condor 99:976–980.
Rappole, J. H., and M. V. McDonald. 1994. Cause and effect in population declines in
migratory birds. Auk 111:652–660.
Rempel, R. S. 2007. Selecting focal songbird species for biodiversity conservation
assessment: response to forest cover amount and configuration. Avian
Conservation and Ecology 2:6.
Robbins, C. S., J. R. Sauer, R. Greenberg and S. Droege. 1989. Population declines in
North American birds that migrate to the Neotropics. Proceedings of the National
Academy of Science 86:7658–7662.
Robichaud, I., and M.-A. Villard. 1999. Do black-throated green warblers prefer
conifers? Meso- and microhabitat use in a mixedwood forest. Condor 101:262–
271.
Robinson, S. K., and D. S. Wilcove. 1994. Forest fragmentation in the temperate zone
and its effects on migratory songbirds. Bird Conservation International 4:233–
249.
Robinson, S. K., F. R. Thompson III, T. M. Donovan, D. R. Whitehead and J. Faaborg.
1995. Regional forest fragmentation and the nesting success of migratory birds.
Science 267:1987–1990.
28
Rompré, G., Y. Boucher, L. Bélanger, S. Côté and W. D. Robinson. 2010. Conserving
biodiversity in managed forest landscapes: the use of critical thresholds for
habitat. Forestry Chronicle 86:589–596.
Rush, S., N. Klaus, T. Keyes, J. Petrick and R. Cooper. 2012. Fire severity has mixed
benefits to breeding bird species in the southern Appalachians. Forest Ecology
and Management 263:94–100.
Sabo, S. R. 1980. Niche and habitat relations in subalpine bird communities of the White
Mountains of New Hampshire. Ecological Monographs 50:241–259.
Salt, W. R. 1973. Alberta vireos and wood warblers. Pub. No. 3, Provincial Museum and
Archives, Edmonton, CA.
Sauer, J. R., J. E. Hines and J. Fallon. 2007. The North American Breeding Bird Survey,
Results and Analysis 1966 – 2006. Version 10.13.2007. USGS Patuxent Wildlife
Research Center, Maryland, USA.
Schmiegelow, F. K. A., and S. J. Hannon. 1999. Forest-level effects of management on
boreal songbirds: the Calling Lake fragmentation studies. In Rochelle, J. A., L. A.
Lehmann and J. Wisniewski, editors. Forest Fragmentation: wildlife and
management implications. Brill, Massachusetts, USA.
Schmiegelow, F. K. A., and M. Mönkkönen. 2002. Habitat loss and fragmentation in
dynamic landscapes: avian perspectives from the boreal forest. Ecological
Applications 12:375–389.
Schmiegelow, F. K. A., C. S., Machtans and S. J. Hannon. 1997. Are boreal birds
resilient to forest fragmentation? An experimental study of short-term community
responses. Ecology 78: 1914-1932.
Schneider, R. R., J. B. Stelfox, S. Boutin and S. Wasel. 2003. Managing the cumulative
impacts of land uses in the western Canadian sedimentary basin: a modeling
approach. Conservation Ecology 7:8.
Schneider, R. R., G. Hauer, D. Farr, W. L. Adamowicz and S. Boutin. 2011. Achieving
conservation when opportunity costs are high: optimizing reserve design in
Alberta’s oil sands region. PLoS ONE 6: e23254.
Sealy, S. C. 1979. Extralimital nesting of Bay-breasted Warblers: response to forest tent
caterpillars? Auk 96:600–603.
Semenchuk, G. P. 1992. The atlas of breeding birds of Alberta. Federation of Alberta
Naturalists, Alberta, CA.
Shulte, L., and G. J. Niemi. 1998. Bird communities of early-successional burned and
logged forest. Journal of Wildlife Management 62:1418–1429.
29
Sillett, T. S., and R. T. Holmes. 2002. Variation in survivorship of a migratory songbird
throughout its annual cycle. Journal of Animal Ecology 71:296–308.
Sleep, J. H., M. C. Drever and K. J. Szuba. 2009. Potential role of spruce budworm in
range-wide decline of Canada Warbler. Journal of Wildlife Management 73:546–
555.
Song, S. J., and S. J. Hannon. 1999. Predation in heterogeneous forest: a comparison at
natural and anthropogenic edges. Ecoscience 6:521–530.
Stadt, J. J., J. Schieck and H. A. Stelfox. 2006. Alberta biodiversity monitoring program
— monitoring effectiveness of sustainable forest management planning.
Environmental Monitoring and Assessment 121:33–46.
Strong, W. L., and K. R. Leggat. 1981. Ecoregions of Alberta. Technical Report T/4.
Alberta Energy and Natural Resources. Government of Alberta, Alberta, CA.
Stutchbury, B. 2007. Silence of the songbirds: how we are losing the world’s songbirds
and what we can do to save them. Walker Publishing Company, Pennsylvania,
USA.
Vanderwel, M. C., S. C. Mills and J. R. Malcolm. 2009. Effects of partial harvesting on
vertebrate species associated with late-successional forests in Ontario’s boreal
region. Forestry Chronicle 85:91–104.
van Frankenhuyzen, K. 1990. Development and current status of Bacillus thuringiensis
for control of defoliating forest insects. Forestry Chronicle 66:498–507.
Venier, L. A., and S. Holmes. 2010. A review of the interaction between forest birds and
eastern spruce budworm. Environmental Reviews 18:191–207.
Venier, L. A., and J. L. Pearce. 2005. Boreal bird community response to jack pine forest
succession. Forest Ecology and Management 217:19–36.
Venier, L. A. and J. L. Pearce. 2007. Boreal forest landbirds in relation to forest
composition, structure, and landscape: implications for forest management.
Canadian Journal of Forest Research 37:1214–1226.
Venier, L. A., J. L. Pearce, D. R. Fillman, D. K. McNicol and D. A. Welsh. 2009. Effects
of spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on boreal
mixed-wood bird communities. Avian Conservation and Ecology 4:3.
Venier, L., S. Holmes and J. Mci. Williams. 2011. Bay-breasted warbler (Setophaga
castanea). In Poole, A., editor. The Birds of North America. Online:
http://bna.birds.cornell.edu/bna/species/206. Accessed 28/10/2012.
Vernier, P. R., F. K. A. Schmiegelow and S. G. Cumming. 2002. Modeling bird
abundance from forest inventory data in the boreal mixed-wood forests of
30
Canada. Pp. 559–571 In Scott, J. M., P. J. Heglund, M. Morrison, M. Raphael, J.
Haufler and B. Wall, editors. Predicting species occurrences: issues of scale and
accuracy. Island Press, California, USA.
Villard, M.-A. 1998. On forest-interior species, edge avoidance, area sensitivity, and
dogmas in avian conservation. Auk 115:801–805.
Villard, M.-A., F. K. A. Schmiegelow and M. K. Trzcinsk. 2007. Short-term response of
forest birds to experimental clearcut edges. Auk 124:828–840.
Westworth, D. A., and E. S. Telfer. 1993. Summer and winter bird populations associated
with five age classes of aspen in Alberta. Canadian Journal of Forest Research
23:1830–1836.
Wilhere, G. F. 2002. Adaptive management in habitat conservation plans. Conservation
Biology 16:20–29.
Wilson, S., S. L. LaDeau, A. P. Tøttrup and P. P. Marra. 2011. Range-wide effects of
breeding- and nonbreeding-season climate on the abundance of a neotropical
migrant songbird. Ecology 92:1789–1798.
Zitske, B. P., M. G. Betts and A. W. Diamond. 2011. Negative effects of habitat loss on
survival of migrant warblers in a forest mosaics. Conservation Biology 25:993–
1001.
31
6.0 APPENDIX 1. POPULATION TRENDS
Black-throated green warbler
Data from the Bird Breeding Survey (BBS) suggest that the black-throated green warbler
is relatively stable nationally, with reported declines of 1.2% annually from 1999–2009
and 0.5 % annually from 1989–2009 (Environment Canada 2012b). Since 1970, the
black-throated green warbler is considered to have shown “little change” (< 25%
decrease), and the reliability of the estimated trend is “high” (status category is likely to
be correct, or at worst within one status category of the actual species status;
Environment Canada 2012b). BBS data for the Boreal Taiga Plains Bird Conservation
Region (BCR 6), which covers most of the species’ breeding range in Alberta, show a
significant increase in population size from 1970–2009 (17.2% annually), but it declined
by 8.3% and 7.0% annually since 1989 and 1999, respectively (Environment Canada
2012a). From 1994–2012, only 102 black-throated green warblers have been captured
and banded at the Lesser Slave Lake Bird Observatory compared to 6024, 4296 and 9054
American redstarts (Setophaga ruticilla), Tennessee warblers (Oreothlypis peregrina)
and yellow-rumped warblers (Setophaga coronata), respectively. These results suggest
substantially lower abundance in this species compared to other more common boreal
songbirds. Significant population declines have been documented in a long-term study in
Alberta (Schmiegelow et al. 1997, Schmiegelow and Hannon 1999, Hannah 2006).
Bay-breasted warbler
Data from the BBS suggest that the Canadian population of the bay-breasted warbler
declined by 3% annually from 1970–2009 and by 5.2 % annually from 1989 to 2009
(Environment Canada 2012b). Since 1970, it is considered to have shown “moderate
decrease” (≥ 25% and < 50% decrease), and the reliability of the estimated trend is “low”
owing mostly to poor coverage of the breeding range (Environment Canada 2012b). BBS
data for BCR 6, which covers most of the species’ breeding range in Alberta, show a
significant increase in population size from 1989–2009, but the importance of this trend
decreases and becomes non-significant when only data from 1999–2009 are considered
(Environment Canada 2012a). From 1994–2012, only 103 bay-breasted warblers have
been captured and banded at the Lesser Slave Lake Bird Observatory compared to 6024,
4296 and 9054 American redstarts, Tennessee warblers and yellow-rumped warblers,
respectively. These results suggest substantially lower abundance in this late-successional
forest specialist compared to other more common boreal songbirds.
Cape May warbler
Data from the BBS suggest that the Canadian population of the Cape May warbler
declined by 5.3% annually from 1999–2009 and 4.2 % annually from 1989–2009
(Environment Canada 2012b). Since 1970, it is considered to have shown “moderate
decrease” (≥ 25% and < 50% decrease), and the reliability of the estimated trend is
“medium” (significant uncertainty about the status category, but is likely to be within one
status category of that assigned, and not off by more than 2 status categories;
Environment Canada 2012b). BBS data for BCR 6, which covers most of the species’
breeding range in Alberta, show a significant increase in population size from 1970–2009
(20.7% annually) and 1989–2009 (23.6%), but population levels have been relatively
32
constant (2.0 % increase) between 1999 and 2009 (Environment Canada 2012a). From
1994–2012, only 132 Cape May warblers have been captured and banded at the Lesser
Slave Lake Bird Observatory compared to 6024, 4296 and 9054 American redstarts,
Tennessee warblers and yellow-rumped warblers, respectively. These results suggest
substantially lower abundance in this late-successional forest specialist compared to other
more common boreal songbirds.
33
List of Titles in the Alberta Species at Risk Management Plan Series (as of March 2014)
No. 1 Long-toed Salamander Conservation Management Plan, 2010-2015.
No. 2 Sprague’s Pipit Conservation Management Plan, 2010-2015.
No. 3 Long-billed Curlew Conservation Management Plan, 2010-2015.
No. 4 Harlequin Duck Conservation Management Plan, 2010-2015.
No. 5 Weidemeyer’s Admiral Conservation Management Plan, 2012-2017.
No. 6 Western Small-footed Bat Conservation Management Plan, 2012-2017.
No. 7 White-winged Scoter Conservation Management Plan, 2012-2017.
No. 8 Bull Trout Conservation Management Plan, 2012-2017.
No. 9 Prairie Falcon Conservation Management Plan, 2012-2017.
No. 10 Black-throated Green Warbler, Bay-breasted and Cape May Warbler Conservation
Management Plan, 2013-2018.