Early indications are that only a quarter of the clutches hatch, but that nest success is quite variable. Because of this variability, further study is needed to determine whether nest success in CRP fields is as good as in alternative habitats. The study of productivity in songbirds also includes an examination of rates of brood parasitism. The northern Great Plains is the center of distribution of the brown-headed cowbird. This species does not build a nest, but lays its eggs in the nest of a host species and leaves them for the host to incubate and to feed and protect the nestlings.
Brood parasitism can reduce the nest success and the number of the host's fledged young.
The overall rate of parasitism was half as high in CRP fields as in WPA fields, suggesting that some feature of CRP fields reduces parasitism by cowbirds. Thus, CRP may have the potential of reducing the harm from parasitism across broad regions of the prairies.