North Central Research Station

Title: Differences in predators of artificial and real songbirds nests: evidence of bais in artificial nest studies

Author: Thompson III, Frank R.; Burhans, Dirk E.

Date: 2004

Source: Conservation Biology. Volume 18. Issue 2. 2004. pp. 372-380

Station ID: JRNL-NC-18

Description: In the two past decades, many researchers have used artificial nests to measure relative rates of nest predation. Recent comparisons show that real and artificial nests may not be depredated at the same rates, but no ne has examined the mechanisms underlying these patterns. We determined differences in predator-specific predation rates of real and artificial nests. We used video cameras to monitor artificial nests baited with quailand plasticine eggs amnd Field Sparrow (Spizella pusilla) and Indigo Bunting (Passerina cyanea) nests in field habitats in central Missouri (U.S.A.). Although daily predaion estimates (all predators pooled0 were similar between artificial andreal nests, predators differed substantially in their depredation of artificial versus real nests. Snakes were the major predator at real nest, and raccons (Procyon lotor) were the major predator at artifical nests. We found strong support for models that distingushed predation between two among three predator groups and between artificial and real nest. There was no snake predation of artificial nests, and the odds of predation of artificial nests was 115-551% (95% confidence interval) and 2-154% of the odds of predation of real nests by mammals and birds, respectively. Artificial nests with plasticine eggs could not be used reliably to identify predators. In several cases plasticine eggs were marked by mice, and raccoons were recorded on video removing the quail egg. Because biases for artificial nests were positive for some predators and negative for other predators (and could be compensating), and potentially existed for all predator groups, conclusions based on artificial nests studies should be suspect even when there is evidence that overall predation rates are similar among real and artificial nests.

Key Words: artificial nests, Field Sparrows, Indigo Buntings, nest predation, predators, raccoons, snakes, songbirds

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Citation

Thompson III, Frank R.; Burhans, Dirk E.  2004.  Differences in predators of artificial and real songbirds nests: evidence of bais in artificial nest studies  Conservation Biology. Volume 18. Issue 2. 2004. pp. 372-380.