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Observer differences in the North American Breeding Bird Survey

Auk

4667_Sauer.pdf
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Abstract

Because count data collected in many bird surveys are only an index to population size, factors that can influence the counts must be identified and incorporated into analyses. Observer quality is often ignored in analyses of population changes from survey data, but observers differ in methods and capabilities and, hence, tend to count different numbers of birds. We assess the consequences of between-observer differences in counts for estimation of population trends in the North American Breeding Bird Survey. Observer differences in numbers of birds counted were found in 50% of the 369 species we examined. For many species, observers in later years tended to count more birds than observers in earlier years, suggesting an increase in observer quality over time. Analysis of population trends from 1966 through 1991 indicates that failure to include observers as covariables in the analysis results in an overly optimistic view of population trends.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Observer differences in the North American Breeding Bird Survey
Series title:
Auk
Volume
111
Issue:
1
Year Published:
1994
Language:
English
Contributing office(s):
Patuxent Wildlife Research Center
Description:
50-62
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Auk
First page:
50
Last page:
62
Number of Pages:
13