Mono Basin Willow Flycatcher Project 2007 Progress Report Chris McCreedy September 2007 PRBO Conservation Science 3820 Cypress Drive, No. 11 Petaluma, CA 94954 [email protected] PRBO Contribution # 1579
Mono Basin Willow Flycatcher Project 2007 Progress Report
Chris McCreedy September 2007
PRBO Conservation Science 3820 Cypress Drive, No. 11
Petaluma, CA 94954 [email protected]
PRBO Contribution # 1579
2
SUMMARY
In 2007, PRBO Conservation Science (PRBO) completed the fifth season of the Mono Basin Willow Flycatcher Project (MBWFP). The project is designed as a long‐term study to investigate the apparent reoccupation of Inyo National Forest (Inyo NF) and Los Angeles Department of Water and Power (LADWP) holdings on lower Rush Creek (Mono County, California) by a population of Willow Flycatchers (Empidonax traillii). Willow Flycatchers are a California State Endangered species (CDFG 1993) and United States Forest Service Region V Sensitive Species. There are only approximately 500 known annual Willow Flycatcher territories remaining in California today (McCreedy and Heath 2004), and approximately 200 known annual Willow Flycatcher territories in the Sierra Nevada (Green et al. 2003). From June through August 2007, PRBO documented 5 territorial males on lower Rush Creek, and five nesting females. Two males were unmated. This marks the third consecutive summer the population has decreased. We did not witness breeding attempts by second‐year returns for the second consecutive year.
Ten territorial adults detected in 2007 are a drop from 12 territorial adults detected in 2006 and 16 territorial adults observed in 2004 (McCreedy 2005). Nest building began on June 13, 2007. Twelve total nests were located on three territories (though two males were unmated, two others were polygynous). Two of these twelve nests fledged young. Of the ten failures, nine were caused by Brown‐headed Cowbird (Molothrus ater) activity.
Five fledglings were raised by five females, a fecundity of 1.0. This is close to the overall
fecundity average from 2001‐2007 (1.11 fledglings per female). Brown‐headed Cowbirds significantly and negatively impacted Willow Flycatcher nest
success at Rush Creek in 2007, as in 2005 and in 2006. Fifty‐eight percent of 2007’s nests were parasitized, and cowbirds directly caused the failure of nine out of twelve nests. Sixty‐four percent of 2005’s and 2006’s Willow Flycatcher nests were parasitized as well (McCreedy 2006). In Research and Management of the Brown‐headed Cowbird in Western Landscapes (1999), a guide to research and management action on cowbirds in the western United States, Smith recommends that managers consider initiating cowbird management programs when the frequency of parasitism consistently exceeds 60% (107).
However, only two of 37 Brown‐headed Cowbird eggs laid in Willow Flycatcher nests
from 2001‐2007 have survived to fledge, and only one of the seven nests that were parasitized in 2007 fledged cowbird young. Though Willow Flycatchers are frequent cowbird hosts on Rush Creek, and though cowbird parasitism almost always results in host nest failure, Willow Flycatchers very rarely raise cowbird eggs to fledge on Rush Creek.
Though Brown‐headed Cowbirds parasitized roughly the same proportion of Willow
Flycatcher nests in 2005 as in 2006 and 2007, the population held a higher fecundity in 2006 and in 2007. This fortunate difference resulted from a sharp decrease in nest failure due to other predators besides cowbirds. Less than ten percent of Willow Flycatcher eggs were lost to non‐cowbird predation in both 2006 and 2007, while roughly one out of three Willow Flycatcher eggs were lost to non‐cowbird predation in 2005 (McCreedy 2006).
3
Ten out of twelve of color‐banded adults present in 2006 returned to Rush Creek in 2007.
However, zero of seven fledglings banded in 2006 returned in 2007, and for the first time, there were no new, unbanded immigrants to enter the population. As such a high number of adults returned in contrast to a total absence of new entries to the population, it is doubtful that the population is suffering decreases in survivorship due to problems on its wintering grounds. Instead, we suspect that extreme drought conditions in 2007 precluded prospecting birds from attempting to breed on Rush Creek. If lower Rush Creek had received its usual input of immigrants and second‐year returns, the population would not have decreased in 2007. None of the ten adults on Rush Creek were born on Rush Creek, unless they were born before nestling banding began in 2003.
To monitor future juvenile recruitment and population dispersal, all five fledged
nestlings were color‐banded in 2007. The entire Willow Flycatcher population at Rush Creek has been color‐banded since 2004, enabling PRBO the rare opportunity to fully assess immigration to Rush Creek and emigration to surrounding riparian areas in 2007 and beyond.
OBJECTIVES The Inyo National Forest has provided much of the funding necessary to the success of the Mono Basin Willow Flycatcher Project. The Grand Family, the Willow Flycatcher Demography Study, the Mono Basin Birding Chautauqua, and the Eastern Sierra Audubon Society have also provided vital funds that have enabled PRBO to pursue the objectives below:
• Conduct Willow Flycatcher nest monitoring on lower Rush Creek, to determine factors affecting productivity, parasitism rates, and predation pressures. Conduct nest‐site vegetation sampling and territory‐scale vegetation sampling to determine Willow Flycatcher nest‐site and territory‐site selection criteria. CURRENTLY 88 NESTS DETECTED FROM 2001‐2007, WITH VEGETATION ASSESSMENTS COMPLETED AT ALL NESTS.
• Conduct territory spot‐mapping on color‐banded individuals to determine population size, phenology, and territory sizes and locations on lower Rush Creek. SEVEN TERRITORIES MAPPED IN 2003, 7 MAPPED IN 2004, 6 MAPPED IN 2005, 7 MAPPED IN 2006, AND 5 MAPPED IN 2007.
• Conduct genetic sampling/analysis and plumage analysis to gain insight into the lower Rush Creek population’s taxonomic status. COMPLETE. INITIAL GENETIC RESULTS FROM UNITED STATES GEOLOGIC SURVEY DEEMED INCONCLUSIVE. PLUMAGE COLORIMETRY PERFORMED ON NINE ADULTS IN 2005, TO BE INCLUDED IN NATIONWIDE USGS WILLOW FLYCATCHER PLUMAGE STUDY. RUSH CREEK SUBSPECIES IDENTITY PENDING THIS USGS ANALYSIS.
4
• Color‐band nestlings and captured adults to determine site fidelity, survivorship, and if nestlings return, recruitment. 17 ADULTS AND 38 NESTLINGS COLOR BANDED (2003‐2007).
• Assist land managers in implementing the Sierra Nevada Forest Plan by incorporating findings into USFS WIFL databases, CDFG WIFL databases, and regional WIFL census networks. ONGOING. DATA WILL BE INCLUDED IN 2005 SIERRA NEVADA WILLOW FLYCATCHER DEMOGRAPHY STUDY. RUSH CREEK NEST DATA USED FOR COMPARISON WITH OTHER INYO NATIONAL FOREST WILLOW FLYCATCHER HABITAT POLYGONS IN 2005. REPORTS ARE HOUSED AT THE UNITED STATES GEOLOGIC SURVEY’S SOUTHWESTERN WILLOW FLYCATCHER CLEARINGHOUSE (http://www.usgs.nau.edu/swwf/reports.htm ) AND BY THE MONO LAKE COMMITTEE (http://www.monobasinresearch.org/images/esrscp/2005wifl.pdf )
BACKGROUND
The Mono Basin Willow Flycatcher Project represents a PRBO, USFS (Inyo NF), and Los Angeles Department of Water and Power (LADWP) collaboration to monitor the recovery of the Willow Flycatcher on lower Rush Creek and in the greater Mono Lake Basin. Lower Rush Creek is under long term, passive restoration after decades of grazing and municipal water diversions. Lower Rush Creek now receives near natural flow, and a grazing moratorium on lower Rush Creek (and across the Mono Basin Scenic Area) has been in place for over ten years (McCreedy and Heath 2004).
PRBO’s Eastern Sierra Riparian Songbird Conservation Project first documented two territorial Willow Flycatcher males on lower Rush Creek in 2000. As described in McCreedy and Heath (2004) and McCreedy (2005), the number of detected territorial adults on lower Rush Creek increased in each year since 2000, with eight in 2001, eleven in 2002, thirteen in 2003, and sixteen in 2004. Notably, the number of detected females has increased from zero in 2000 to three in 2001, four in 2002, six in 2003, and eight in 2004 (only five females were present on lower Rush Creek in 2006). This is the only known breeding population of Willow Flycatchers in the Inyo National Forest.
Over the twentieth century, Willow Flycatchers have experienced precipitous declines across California, particularly in the Sierra Nevada and along the Colorado River (Craig and Williams 1998, Serena 1982). After several trips to the Mono Basin and Eastern Sierra in the early twentieth century, biologist Joseph Grinnell termed Willow Flycatchers to be “fairly common”, and noted nesting material carries near the Mono Inn, on Mono Lake’s western shore (Grinnell and Dixon field notes at the Museum of Vertebrate Zoology). In addition, several Rush Creek nesting records exist prior to the initiation of municipal diversions to Los Angeles in 1941 (unpublished records at the Western Foundation of Vertebrate Zoology). However, subsequent Willow Flycatcher nesting records in the Mono Basin are nearly nonexistent. David Gaines confirmed the most recent, nearby Willow Flycatcher breeding in Mono County at Mammoth Creek in the early 1970s (Gaines 1992). Prior to their detection by PRBO biologists in 2000, singing Willow Flycatchers had not been found on lower Rush Creek since 1982 (Joe Jehl, personal communication). Due to these population declines, the USFS Region V has placed a high research priority on Sierra Nevada Willow Flycatcher populations, and the Mono Basin Willow Flycatcher Project complements larger research efforts in the northern Sierra Nevada near
5
Truckee (Mathewson et al. 2005), and in the southern Sierra Nevada near Weldon (Whitfield et al. 1997).
The lower Rush Creek population has expressed nest site and territory habitat attributes anomalous to other Willow Flycatcher populations in California. These attributes include a predilection for Woods’ Rose (Rosa woodsii) (through 2007, 88 out of 88 located nests have been built in Woods’ Rose), and a lack of territory and nest site correlation to surface water (McCreedy and Heath 2004). Research into the use of these anomalous habitats will identify alternatives to typically surveyed habitats, which will assist the USFS and California Department of Fish and Game (CDFG) in the conservation of this endangered species. Continued monitoring of the Rush Creek population will provide a unique glimpse into the establishment and survival of a small, isolated population of an endangered species
METHODS At 37.93 N° and 119.07° W, lower Rush Creek spans the final seven kilometers of Rush Creek’s descent to Mono Lake, extending from the “Narrows” cataract to the Rush Creek – Mono Lake delta. Rush Creek drops from 2011 meters above sea level at the Narrows to 1945 meters above sea level at its delta with Mono Lake. Surveys began June 7, 2006, and ended August 28, 2007. Initial surveys consisted of territory spot mapping in accordance with International Bird Conservation Committee recommendations (IBCC 1970) and following Ralph et al. (1993). Lower Rush Creek was divided into four sections of roughly equal size, which were each covered roughly once every four days. All Willow Flycatcher detections were marked with a Garmin GPS V receiver and added to GIS coverage to maximize spot‐mapping accuracy. Sex and age of detected adults were noted when possible, and color‐band identifications were recorded whenever possible. NEST MONITORING, NEST VEGETATION ASSESSMENTS, AND NEST ANALYSES Nests were located and monitored at least once every four days, following protocols described in Martin and Geupel (1993) and Martin et al. (1997). All nests were located during the building or egg‐laying phase. On each visit to the nest, nest contents were recorded, and Brown‐headed Cowbird parasitism noted. After nesting was complete, 5 m‐radius vegetation assessments about each nest were conducted also following Martin (1997).
Nest and non‐nest assessments included absolute cover estimates of shrub cover, non‐woody cover, and groundcover. Groundcover was broken into “litter”, “bare ground”, “water”, and “rock”. Relative cover (by species) of absolute shrub and non‐woody cover were estimated; relative species covers were then multiplied by absolute shrub and non‐woody cover to give by‐species absolute cover estimates for analysis. Numbers of “tree” stems (by species) were counted in 11.3 m‐radius plots around each nest. To qualify as a “tree”, a plant must have been over 5 m in height and have a diameter at breast height (DBH) of at least 8 cm. Canopy measurements included: four averaged densiometer readings taken at cardinal points at the nest or non‐nest point to measure foliage cover above the nest; “canopy height”, the maximum average height of the canopy within 11.3 m of the nest, and “canopy cover”, the percent of the 11.3 m‐radius plot
6
covered by vegetation greater than 5 meters in height (regardless of DBH). Distance‐to‐water measurements and riparian‐width measurements were measured using USFS‐provided aerial photographs projected onto ArcGIS 9.2 (ESRI 2006) in cases when accurate field measurements were not possible.
The majority of 2001‐2007 nests were located early in the building stage, and all save one
(not used in egg fate analysis) were found prior to clutch completion. Thus the fates of all eggs are known, within reason (Figure 4). Eggs that disappeared in coincidence with the appearance of a new BHCO egg were assumed to be ejected by Brown‐headed Cowbirds. If a female Brown‐headed Cowbird was observed within 3 m of an active nest whose eggs were later depredated, that loss was assigned to cowbird activity. Eggs that did not hatch in parasitized nests were presumed to not hatch due to cowbird parasitism. All young dubbed to be fledged were observed after fledging, and young not observed after fledging were counted as depredated from the nest.
Mayfield total nest survival estimates were calculated following Mayfield (1975, 1961).
Summary statistics and mean comparisons for vegetation measurements were calculated using STATA 8.0’s two‐sample mean comparison calculator for unequal variances (Stata Corp 2003). COLOR‐BANDING AND PLUMAGE COLORIMETRY
Target‐netting began in early July 2007. We used a combination of passive mist‐netting (setting 5 m or 2 m mist nets across common flight paths on territories) and active mist‐netting (using hidden speakers placed near nets and playing a series of vocalizations to bring flycatchers to nets).
Beginning in July 2005, PRBO switched to using one metal FWS band on one leg, and one
pinstriped metal band (with two colors applied to the metal) on the other leg (previously, two shaped, colored celluloid bands were placed opposite the FWS band). Pinstriped metal bands have been shown to dramatically decrease band‐induced injuries to Empidonax flycatchers (Koronkiewicz et al. 2005) and were graciously provided by the Southern Sierra Research Station and by SWCA Consultants. As in previous years, all adults were banded with a metal FWS band on the right leg, and all young were banded with a metal FWS band on the left leg. Beginning in 2007, we began using red anodized metal FWS bands, to increase color combination numbers. These red anodized bands are signified by Rf (red federal).
PRBO and the Inyo NF have partnered with the United States Geologic Survey to determine the taxonomic status of the Rush Creek Willow Flycatcher population. Rush Creek lies at the confluence of three Willow Flycatcher subspecies ranges (Empidonax traillii adastus, E.t. extimus, and E.t. brewsteri (Unitt 1987), and the taxonomic identity of the Rush Creek population remains unknown. In 2005, the USGS analyzed blood from three Rush Creek Willow Flycatchers sampled by PRBO in 2003. However, mitochondrial DNA sequences from Rush Creek birds are of a type not restricted to any particular Willow Flycatcher subspecies, and thus blood sampling produced inconclusive results (Eben Paxton, personal communication). However, the USGS has devised another method to determine Willow Flycatcher subspecies identity, using a Minolta colorimeter (Paxton et al. 2005) to quantitatively measure Willow Flycatcher plumage color. The USGS considered the Rush Creek geographic location important enough for inclusion in a United States‐wide colorimetric study of Willow Flycatcher
7
plumage variation by subspecies, and PRBO assisted one of the study’s principal investigators in the capture and measurement of one female in July 2005. A better sample size was necessary, and PRBO captured and measured eight additional Rush Creek adults (with the colorimeter on loan) in late July 2005. The results from the Rush Creek sample will be included in the USGS study.
RESULTS AND DISCUSSION We detected five territorial males during the course of the 2007 breeding season on lower Rush Creek. Five females were detected as well. Two males, the territory 7 male (Blue‐Green/Silver, or BG/S) and the territory 4 male (Yellow‐Orange/Silver, or YO/S) were unmated. Both BG/S and YO/S have been present for multiple seasons on Rush Creek (BG/S since 2006, and YO/S since 2005), but while each has in the past “stolen” a second female from a polygynous male, these females already had laid clutches when this occurred. Thus while it cannot be known for certain, it is unlikely that either of these males has ever sired eggs on Rush Creek. Territory numbers refer to geographic locations of previous territories in previous years – thus there exist “territory 6 and territory 7” males, despite a total population of only five males.
Figure 1. Number of detected territorial Willow Flycatchers on Rush Creek, Mono County, CA 2000‐2007. The entire lower Rush Creek corridor was first surveyed in 2002.
024681012141618
2000
2001
2002
2003
2004
2005
2006
2007
WIFL Males
WIFL Females
WIFL
Figure 2 depicts the five 2007 territories. Two of the twelve 2007 nests were on Inyo NF land. Territories 1, 5, and 7A straddled the LADWP/Inyo NF property boundary, while the remaining 10 nests and 3 territories were on LADWP land.
8
Figure 2. Willow Flycatcher territories on Rush Creek, Mono County, 2007. Territory numbers are referred to in subsequent tables and text. The territory 7A male abandoned his first territory and subsequently sang for short periods at 7B and 7C, without attracting a mate.
9
NESTS We located and monitored twelve nests for five females in 2007.
Table 1. Willow Flycatcher color combinations, dates initiated, and nest outcomes at lower Rush Creek, 2007. Numbered territories correspond to Figure 2. Note: Territory 5 female (BO/S) = YY/S in previous years, old celluloid bands were removed and new split‐metal band applied in 2007.
Territory Male color combination
Female color combination
Date of first egg
Date of fledge or failure Outcome
1 RM/S RY/S 22 June 13 July Fledged a BHCO. One WIFL egg fails to hatch, 3
WIFL nestlings perish due to larger BHCO.
2 OK/S GK/S ‐ ‐ Abandoned while building, female cowbird seen
within 3 m of nest while deconstructing.
OK/S GK/S ‐ ‐ Abandoned while building, female cowbird seen
within 5 m of nest while deconstructing.
OK/S GK.S 25 June 3 July BHCO female removes sole WIFL egg, then
WIFL female abandons BHCO egg.
3 OO/S GO/S ‐ ‐ Abandoned building, female BHCO within 3 m
of nest.
OO/S GO/S 30 June 14 July Female BHCO removes a WIFL egg, GO/s
abandons BHCO nestling and two WIFL eggs.
OO/S GO/S 24 July 21 August Fledged two young.
4 YO/S ‐ ‐ ‐ Unmated
5 OK/S BO/S ‐ ‐ Buried BHCO egg.
OK/S BO/S 19 June 20 June BHCO removes WIFL egg, WIFL abandons.
OK/S BO/S ‐ ‐ Buried BHCO egg.
OK/S BO/S 29 June 26 July Fledges 3 young.
6 OO/S RK/S 22 June 18 July Depredated one young, one BHCO and two
WIFL eggs fail to hatch.
7 BG/S ‐ ‐ ‐ Unmated Colors Used: Rf= Red federal anodized band; R= Red; M= Mauve; B=Blue; W=White; G=Green; K= Black; O=Orange; Y=Yellow; S= Silver FWS Band. Combinations are read left leg/right leg, and body to toe. BHCO=Brown‐headed Cowbird, and WIFL=Willow Flycatcher.
Though Mayfield total survival, a measure of nest success, was higher in 2007 than in 2006 (Figure 3), fecundity was lower (1.0 fledglings per female in 2007 versus 1.2 in 2006), and egg fate proportions were roughly the same in each year (Figure 4). The lower fecundity of 2007 (in spite of higher nest success) can be attributed to the longer lifetime of failed nests in 2007, which slightly increased Mayfield survival estimates in spite of the nests’ eventual failure.
10
Figure 3. Mayfield total nest survival on lower Rush Creek, by year, and all nests combined (2003‐2007).
Mayfield total survival for WillowFlycatchers on Lower Rush Creek
00.1
0.20.3
0.40.5
0.6
2003 2004 2005 2006 2007 ALL
WIFL Mayfield TotalNest Survival
Figure 4. Fates of 125 Willow Flycatcher eggs at lower Rush Creek, 2001‐2007.
Willow Flycatcher Egg Fates on Rush Creek, 2001 ‐2007
0%
20%
40%
60%
80%
100%
2001 (n=8)
2002 (n=14)
2003 (n=28)
2004 (n=18)
2005 (n=31)
2006 (n=26)
2007 (n=17)
unhatched, unknowncause BHCO
predation
fledged
11
BANDING and RESIGHTING Ten of twelve (83%) 2006 color‐banded adults returned in 2007. Zero of seven (0%) 2006 color‐banded young returned in 2007, the first time zero juveniles were seen the following season in the course of our study.
To coordinate with USFS Willow Flycatcher research in the Sierra Nevada, color combinations and estimated arrival and departure dates are presented in Table 2. One hundred percent of the population’s adults are positively known to be at least four years old, and at least six adults (60%) are known to be at least six years old. The Willow Flycatcher longevity record is eight years and eleven months, though older birds may have been recorded (Mary Whitfield, personal comm. and USGS Bird Banding Lab, http://www.pwrc.usgs.gov/bbl/homepage/long3930.htm ).
Table 2. Color combinations observed in 2007 on Rush Creek. Color combination abbreviations described in Table 1. “AHY” = After Hatch Year, and “HY” = Hatch Year. Asterisk (*) denotes bird that was likely present before 2007 surveys began on 7 June. Carrot (^) denotes bird that was present after surveys ended on 28 August.
Territory Age/Sex Color Combination First
Encountered/Fledge Last Seen
1 After 7th year male RM/S 10 June* 15 July
After 4th year female RY/S 15 June 14 July
2 After 8th year female GK/S 10 June* 19 July
3 After 6th year male OO/S 7 June* 23 August
After 5th year female GO/S 6 June* 28 August^
HY Rf/GR 21 August 18 September
HY Rf/OB 21 August 28 August^
4 After 4rd year male YO/S 10 June* 15 July
5 After 7th year male OK/S 10 June* 28 July
After 7th year female YY/S changed to BO/S 10 June 28 July
HY S/GM 23 July 28 July
HY S/WG 23 July 28 July
HY S/WY 23 July 28 July
6 After 5th year female RK/S 12 June 29 July
7 After 4th year male BG/S 10 June 16 July
12
ACKNOWLEDGEMENTS
We are grateful for the financial and logistical support of the Inyo National Forest, California Audubon, the Grand Family, the Mono Basin Chautauqua Committee, the Mono Lake Committee, Eastern Sierra Audubon Society, Mono Lake Tufa State Reserve, California Department of Fish and Game, and the University of Nevada‐Reno. LADWP provided access to their Rush Creek lands. Gary Milano provided aerial photographs, insight into the grazing history at Inyo NF polygons, and general support. Mary Whitfield of the Southern Sierra Research Station provided hours of target netting, color banding, and blood sampling assistance. Eben Paxton of the USGS contributed genetic analysis. Eben Paxton and Tom Koronkiewicz provided equipment for colorimetry. Sacha Heath, Katie Fehring, Selena Humphreys, Libby Porzig, Wendy Willis, Helen Green, and Tom Koronkiewicz assisted with target netting, color‐banding, and colorimetry. Jessi DeLong, Elin Ljung, Sarah Jane Pepper, and George Appel assisted with nestling banding. Michael Lester and George Appel assisted with off‐site searches for dispersing birds. This is PRBO Contribution # 1579.
LITERATURE CITED CALIFORNIA DEPARTMENT OF FISH AND GAME. 1993. Annual report on the status of California state‐listed threatened and endangered animals and plants. http://www.dfg.ca.gov/hcpb/species/t_e_spp/tebird/tebirda.shtml CRAIG, D. AND WILLIAMS, P. L. 1998. Willow Flycatcher (Empidonax traillii), in California Partners In Flight riparian conservation plan. http://www.prbo.org/CPIF/Riparian/Wifl.html. ESRI. 2000. ArcView Geographic Information System version 3.2a. Environmental Systems Research Institute, Inc. Redlands, CA. GAINES, D. 1992. Birds of Yosemite and the East Slope, 2nd ed. Artemisia Press, Lee Vining, CA. GREEN, G.A., BOMBAY, H.L., AND MORRISON, M.L. 2003. Conservation Assessment of the Willow Flycatcher in the Sierra Nevada. USDA Forest Service. Vallejo, CA. 62 pp INTERNATIONAL BIRD CONSERVATION COMMITTEE. 1970. An international standard for a mapping method in bird census work recommended by the International Bird Census Committee. Audubon Field Notes 24:722‐726. KORONKIEWICZ, T.J., PAXTON, E.H., AND SOGGE, M.K. 2005. A technique to produce avian color bands for avian research. J. Field Ornithology. 76:94‐97. MARTIN, T.E., AND GEUPEL, G.R. 1993. Nest monitoring plots: Methods for locating nests and monitoring success. J. Field Ornithology. 64:507‐519. MARTIN, T.E., PAINE, C., CONWAY, C. J., HOCHACHKA, W. M., ALLEN P., AND JENKINS, W. 1997. The Breeding Biology Research and Monitoring Database (BBIRD) Field Protocol. Univ. of Montana Coop. Unit, Missoula, MT. http://pica.wru.umt.edu/BBIRD/protocol/protocol.html.
13
MATHEWSON, H.A., LOFFLAND, H., AND MORRISON, M.L. 2005. 2004 Annual report and preliminary demographic analysis for Willow Flycatcher monitoring in the Central Sierra Nevada: in partial fulfillment of Cost Share Agreement 04‐CR11052007‐056. University of Nevada‐Reno and United States Forest Service Region V, 38pp. MAYFIELD, H. 1975. Suggestions for calculating nest success. Wilson Bull. 87: 456‐466. MAYFIELD, H. 1961. Nesting success calculated from exposure. Wilson Bull. 73:255‐261. MCCREEDY, C. 2006. Mono Basin Willow Flycatcher Project: 2006 Progress Report. Point Reyes Bird Observatory (Contrib. 1512), 3820 Cypress Drive, No. 11, Petaluma, CA 94954. MCCREEDY, C. 2005. Mono Basin Willow Flycatcher Project: 2005 Progress Report. Point Reyes Bird Observatory (Contrib. 1298), 3820 Cypress Drive, No. 11, Petaluma, CA 94954. MCCREEDY, C. AND HEATH, S.K. 2004. Atypical Willow Flycatcher Nesting Sites in a Recovering Riparian Corridor at Mono Lake, CA. Western Birds 35:197‐209. PAXTON, E.H., CAUSEY, C.F., KORONKIEWICZ, T.J., SOGGE, M.K., JOHNSON, M.J., MCCLOUD, M.A., UNITT, P., WHITFIELD, M.J. 2005. Assessing variation of plumage coloration within the Willow Flycatcher: a preliminary analysis. U.S. Geological Survey Report. RALPH, C.J., GEUPEL, G. R., PYLE, P., MARTIN, T. E., AND DESANTE, D. F. 1993. Field methods for monitoring landbirds. USDA Forest Service Publication: PSW‐GTR 144. SERENA, M. 1982. The status and distribution of the Willow Flycatcher (Empidonax traillii) in selected portions of the Sierra Nevada, 1982. Wildlife Mgmt. Branch Admin. Rep. 82‐85. Calif. Dept. Fish & Game, Sacramento. SMITH, J.N.M. 1999. The basis for cowbird management: host selection, impacts on hosts, and criteria for taking management action. Studies in Avian Biology No.18:104‐108. STATA CORPORATION. 2003. Stata statistical software, Release 8.0. Stata Corporation, College Station, TX. UNITT, P. 1987. Empidonax traillii extimus: an endangered subspecies. Western Birds: 18:137‐162. WHITFIELD, M.J., K. ENOS, AND S. ROWE. 1997. Reproductive response of the Southwestern Willow Flycatcher (Empidonax traillii extimus) to the removal of Brown‐headed Cowbirds. Draft Report prepared for U.S. Army Corps of Engineers, Sacramento District, and Calif. Dept. of Fish and Game, Wildlife Manage. Div., Bird and Mammal Conservation Program.
14