Egg Coloration and Recognition of Conspecific Brood Parasitism in Eastern Bluebirds.

Siefferman, Lynn

Individual eastern bluebird ( Sialia sialis) females produce clutches of eggs with unique coloration and older females and females in better body condition lay more pigmented blue-green eggs. Conspecific brood parasitism in this species is not uncommon and bluebirds occasionally reject what appear to be normal eggs by moving them to the periphery of the nest. I used UV-visual reflectance spectrometry to objectively measure coloration of eggs and nest material. To estimate the conspicuousness of the trait, I calculated the contrast between eggs and background nest material. I found high achromatic and chromatic contrast between the coloration of eggs and of the nests, suggesting that bluebird eggs are highly conspicuous. To test the hypothesis that expression of blue-green coloration eggs facilitates recognition of eggs laid by conspecific brood parasites, I cross-fostered individual eggs into host nests during egg laying and monitored the fate of those eggs. I found no support, however, for the hypothesis that egg coloration facilitates discrimination of parasitic eggs from host eggs.

PROTECTIVE coloration (Biology); BIRD eggs; BROOD parasitism; PREDATION; TURDIDAE; EASTERN bluebird

Ethology, 2006, Vol 112, Issue 9, p833

0179-1613

Academic Journal

10.1111/j.1439-0310.2006.01229.x