Tucson’s Birds: Why Scale Matters Rachel McCaffrey
Dec 17, 2015
Tucson’s Birds:Why Scale Matters
Rachel McCaffrey
In developed areas, factors controlled by humans are important to determining whether native bird species persist
• Vegetation– Volume– Composition– Diversity
• Land-use – Types– Arrangement– Intensity
Bird• Occurrence• Abundance• Diversity• Composition
• Volunteer-based bird survey program
• Abundances and distribution
• Annual, citywide count~ 1,000 sites, 1/km2
• Quarterly, “Park” count~ 200 sites at 30 locations
Annual Survey Sites10 km ±
Park Monitoring Sites
Research Focus
Birds and habitat features in residential developments: an issue of scale
What we know:• Urban areas have less diverse groups of birds• ↑ in non-native species• Some types of development support more
native birds
Scale is important!
urban areas = heterogeneity and disturbance(Hostetler 1999)
(Hostetler 1999)
Local vs. landscape features
Individual yards Surrounding area
Species Dependent!
Why is this important?
which features @ which scale
=
species and scale-specific
management guidelines• homeowners
• neighborhoods• planners
Study Design
Randomly selected 300 sites
Bird surveys
• 5-minute point count, 40 m radius• Each site surveyed 4 times, March 15 – June 15• 10 species
Habitat features - Local
• 0.5-ha circular plot (40 m radius)
– Represents typical residential lot– On-site measurements
• Features measured based on known habitat requirements of species
Habitat features - Local
• Number of: – cholla cacti (> 1m)– saguaro cacti (> 2m)– mesquite and palo verde trees (> 3m)– native thorn trees (> 2m)– large “roost” trees (> 5m)– palm trees (> 5m)– homes
• Presence of:– desert mistletoe– wash
• Percent of vegetation that is native
Habitat features - Landscape
• 50-ha circular plot (399 m radius)– Represents typical neighborhood/development– Used digitalized aerial photographs & GIS
• Features measured based on habitat requirements and management potential
• number of washes• percent of area in open space• percent of area covered by lawn• presence of natural area > 5 ha
Habitat features - Landscape
Regression analyses:
Which features are most important for each species at each scale?
Variance decomposition:
Was a species most influenced by features at the local or landscape scale?
Data Analysis
Results
Average of 5.5 species/site
21.6% of sites 87.8% of sites
Results – Local Scale
• number of thorn trees• number of cholla• number of mesquite and palo verde trees • overall percent native vegetation• number of homes
Results – Landscape Scale
• number of washes (4)• percent of area in open space (6)• percent of area covered by lawn (3)
Results - Scale
Species most influenced by local scale features:• Cactus wren
• Curve-billed thrasher
• Phainopepla
Cactus wren
0
20
40
60
80
100
0 1-3 4-6 7-9 10-12 13-15 16-18 19+Number of cholla
Per
cent
of
site
s w
ith
cact
us
wre
ns
Results - Scale
Species most influenced by
landscape scale features:• Ash-throated flycatcher
• Lesser goldfinch
Ash-throated flycatcher
0
10
20
30
40
0 1 2 3 4+
Number of washes
Percent of sites withAsh-throated Flycatchers
Results - Scale
Species most influenced by shared associations: • Gambel’s quail
• Gila woodpecker
• Northern cardinal
• Pyrrhuloxia
• Verdin
Pyrrhuloxia
• Influenced most by shared associations across scales……• Local: % native vegetation• Landscape: % open, % lawn (-)
E.J. Peiker
The Influence of Scale
• Importance of habitat features varied by species and scale
• Cross-scale interactions
Need scale-specific
management strategies!
Local scale implications
Individual homeowners can have an impact!
• plant thorn trees, cholla, native trees
Landscape scale implications
Neighborhood groups and developers of master-planned communities can take broader actions:
• ban/limit lawns
• promote native landscaping
• incorporate open space
• restore riparian areas
A multi-scale approach
Homeowner plants thorn trees
Development incorporates open space
Regional planning efforts to maintain riparian networks
In Conclusion…..
The persistence of many native birds in urban areas will depend on:• Identifying key habitat features • Understanding the relevant scales • Targeting management efforts