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Estimating Populations of Nesting Brant Using Aerial Videography

R. Michael Anthony, William H. Anderson, James S. Sedinger and Lyman L. McDonald
Wildlife Society Bulletin (1973-2006)
Vol. 23, No. 1 (Spring, 1995), pp. 80-87
Published by: Wiley on behalf of the Wildlife Society
Stable URL: http://www.jstor.org/stable/3783199
Page Count: 8
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Estimating Populations of Nesting Brant Using Aerial Videography
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Abstract

We mounted a video camcorder in a single-engine aircraft to estimate nesting density along 10-m wide strip transects in black brant (Branta bernicla nigricans) colonies on the Yukon Delta National Wildlife Refuge, Alaska during 1990-1992. A global positioning system (GPS) receiver was connected to the video recorder and a laptop computer to locate transects and annotate video tape with time and latitude-longitude at 1-second intervals. About 4-5 hours of flight time were required to record 30-40 minutes of video tape needed to survey large (>5,000 nests in ≥10 km2) colonies. We conducted ground searches along transects to locate and identify nests for determining detection rates of nests in video images. Counts of nests from video transects were correlated with actual numbers of nests. Resolution of images was sufficient to detect 81% of known nests (with and without incubating females). Of these, 68% were correctly identified as brant nests. The most common misidentification of known nests was failure of viewers to see the nest that the detected bird was incubating. Unattended nests with exposed eggs, down-covered nests, and nesting brant, cackling Canada geese (Branta canadensis minima), and emperor geese (Chen canagica) were identified in video images. Flushing of incubating geese by survey aircraft was not significant. About 10% of known nests were unoccupied in video images compared to 16% unoccupied nests observed from tower blinds during periods without aircraft disturbance.

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