Whereas most host species parasitized by Brown-headed Cowbirds (Molothrus ater) accept cowbird eggs in their nests, others reject the foreign eggs or desert parasitized clutches. Chipping Sparrows (Spizella passerina) are a nest deserting host of cowbirds, but many of their nests continue to be incubated with cowbird eggs suggesting that cowbird eggs per se do not necessarily trigger desertion. We demonstrate that encounters with an adult female brood parasitic cowbird rather than with a cowbird egg in the nest, elicit nest desertion. We observed that a total of 33 (67.3%) of 49 nests were naturally parasitized in Illinois. Parasitized nests fledged less than one third of the number of host young than unparasitized nests did, indicating that parasitism is extremely costly in this species and that an evolved response to parasitism would likely spread through the population over time.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.