Effects of stage of the breeding cycle on sage sparrow detectability

Publication Type:

Journal Article

Authors:

Best, Louis B.; Petersen, Kenneth L.

Source:

Auk, American Ornithologists' Union, Volume 99, Issue 4, p.788-791 (1982)

Call Number:

A82BES01IDUS

URL:

https://sora.unm.edu/node/23761

Keywords:

Amphispiza belli, Field Sparrow, Sage sparrow, Spizella pusilla

Abstract:

Among the myriad of factors potentially affecting the accuracy of bird census procedures are seasonal changes in detectability that correspond with different stages in the birds' breeding cycle. If detectability is influenced by the stage of the breeding cycle, then "perceived" changes in size within a single population or disparities in size among different populations may be only sampling artifacts rather than indications of actual differences in population density. In particular, this poses a problem when the census interval for a given study is long or when the results from more than one study are compared in which counts were conducted at different times in the season. Effects of the stage of the breeding cycle on bird detectability have been largely ignored, although Best has quantified these for the Field Sparrow (Spizella pusilla). During an intensive study of the breeding ecology of passerines occupying a sagebrush-grassland community, we had the opportunity to make a similar evaluation for the Sage Sparrow (Amphispiza belli). Those results are reported herein. The study area is located within the western boundary of the Idaho National Engineering Laboratory site in southeastern Idaho.