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- Title
Effect of count duration on abundance estimates of Black-capped Vireos.
- Authors
Cimprich, David A.
- Abstract
Distance sampling applied to point count surveys (point transects) has become a common method for estimating the absolute abundance of birds. When conducting point transects, detections of focal species are typically recorded during a fixed time interval. However, count duration has varied among studies and the effect of such variation on the resulting abundance estimates is unclear. My objective was to examine the effect of count duration on abundance estimates of male Black-capped Vireos ( Vireo atricapilla). The abundance of these vireos in a 349-ha area in central Texas was estimated using 3-, 5-, and 6-min point transects and results were then compared to actual number present as determined by banding and territory mapping. The 3-min counts provided an estimate that was 26% greater than the actual number of male Vireos present ( N= 201), but this number was within the corresponding 95% confidence interval ( N= 157–413). Confidence intervals for the 5- and 6-min counts did not include the actual number of vireos present. The shortest count duration may have provided the most accurate abundance estimate because male Black-capped Vireos are typically active, sing intermittently, and sometimes move tens of meters between songs. Thus, shorter-duration counts may also yield the most accurate abundance estimates for other species that exhibit similar behavior. However, because behavior varies among species, I recommend that investigators collect preliminary data to establish an appropriate count duration when accurate estimates of absolute, rather than relative, abundance are important.
- Subjects
BLACK-capped vireo; VIREOS; VIREONIDAE; BELL vireo; CASSIN'S vireo; PHILADELPHIA vireo
- Publication
Journal of Field Ornithology, 2009, Vol 80, Issue 1, p94
- ISSN
0273-8570
- Publication type
Article
- DOI
10.1111/j.1557-9263.2008.00188.x