Bicknell's Thrush Habitat Selection and Demographics

Bicknell’s Thrush Habitat and Demographics
Kent McFarland
Chris Rimmer
Judith Scarl

Bicknell’s Thrush
Rare
global population < 100,000 individuals
Ranges restricted and fragmented
occupies habitat “islands”
At risk
population declines
multiple habitat threats in N. America
severe, ongoing winter habitat loss
Reclusive and Enigmatic
many obstacles to understanding status
few baseline population data

Partners In Flight = North America Watch List IUCN Red List = Vulnerable ABC/Audubon WatchList = Red List Canada = Threatened USFWS = Special Concern ME, NH, NY, VT = Special Concern www.bicknellsthrush.org

-15% 2002 - 2009 -17% 2002 - 2009 -7% annual decline 1993-2005

95% of the records occurred in spruce-fir habitat above threshold that drops in a linear fashion 81 m for every degree increase in latitude 0.05 Quantile Regression

Occupancy Estimation and Modeling Using Repeated Counts 110 000 101 011 111 010

Occupancy Estimation and Modeling Using Repeated Counts

Bicknell’s Thrush may be able to persist in marginal landscape contexts if local habitat is good and vice versa Both scales are important for determining occupancy patterns

Predicted abundance of Bicknell’s Thrush at a site in Quebec derived from the best model (elevation + canopy density + forest type). Repeated counts analyzed using N-mixture model of Royle (2004) and Kéry et al (2005)

Calculation of Detection Probability for Surveys Necessary Site in Quebec Mountain Bird Watch in Vermont

Monitoring Methods
Nests located with telemetry (~80%)
Efficient, minimizes disturbance, less bias
outfitted with a small radio transmitter

r r r r r r r r r r 5 Males - 95% KHR Bicknell’s Thrush Kernel Home Range 2 Females - 95% KHR

More than 60% of the nests were within 50m of a ski trail or work road edge.

Annual Survivorship Estimation Program MARK
Global model contained:
Study mountains (Mansfield, Stratton, Gaspe)
Study areas with abrupt linear edges from ski trails and work roads vs. natural areas
Male, Female and SY, ASY
Possible that SY adults emigrate after their first breeding season while older birds tend to have very high site fidelity, we used transient in our modeling which compares Φ and t in year +1 as one group (transients) and year 2+ as a second group.
p(site*habitat) chosen a priori .

Mark-Recapture Annual Survivorship Models Model AICc Delta AICc Weight {Phi(trans*site) p(site*sex*hab)} 1691.032 0 0.70549 {Phi(yearAD*trans*site) p(site*sex*hab)} 1693.275 2.24 0.22976 {Phi(trans*site*hab) p(site*sex*hab)} 1697.412 6.38 0.02903 {Phi(trans) p(site*sex*hab)} 1698.124 7.09 0.02034 {Phi(trans*hab) p(site*sex*hab)} 1700.852 9.82 0.0052 {Phi(trans*site*sex) p(site*sex*hab)} 1701.187 10.16 0.0044 {Phi(trans*sex) p(site*sex*hab)} 1702.066 11.03 0.00283 {Phi(yearAD*trans*hab) p(site*sex*hab)} 1703.27 12.24 0.00155 {Phi(yearAD*trans) p(site*sex*hab)} 1703.878 12.85 0.00115 {Phi(trans*sex*hab) p(site*sex*hab)} 1707.4 16.37 0.0002

Population Growth Rate Two-stage Leslie Matrix model

Relative Contributions of Survival and Fecundity to Population Growth Rate Model elasticities indicate that ASY female survival had a greater effect on lambda than did fecundity in most cases

Acknowledgements
We are grateful to the many field biologists and volunteers who dedicated countless hours of field work under conditions that were often difficult.
We also thank the Stratton Mountain Resort, the Mt. Mansfield Company, for valuable logistic support.
VCE’s work on this project through September of 2007 was conducted under the Vermont Institute of Natural Science, to whom we express thanks for its institutional support.
Funding was generously provided by the Conservation and Research Foundation, the Davis Conservation Foundation, the Frank and Brinna Sands Foundation, the National Fish and Wildlife Foundation, The Nature Conservancy - Vermont Chapter, the Nuttall Ornithological Club, the Philanthropic Collaborative, the Stratton Foundation, the Stratton Mountain Resort, the Thomas Marshall Foundation, the Wallace Genetic Foundation, a State Wildlife Grant through the Vermont Fish and Wildlife Department, the Vermont Monitoring Cooperative, USDA Forest Service Northeastern Research Station, U.S. Fish and Wildlife Service, the William P. Wharton Trust, and many individual donors.

Bicknell's Thrush Habitat Selection and Demographics

by Vermont Center for Ecostudies on May 10, 2011

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Bicknell’s Thrush Habitat Selection and Demographics — Presentation Transcript

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