Nesting Success Calculated from Exposure

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. IN reporting the nesting success of birds, it is customary to give the numbe of nests and eggs in the sample, the number of eggs that hatch, the numbe of young birds fledged, and various percentages derived from these. In my analysis of the nesting success of the Kirtland's Warbler (Dendroica kirtlandii) I had shortcomings and subtleties in my data that could not be treated satisfactorily by the customary methods. Most serious of these prob-lems was the fact that many of the nests in my sample had not been found un-til after incubation had begun. That others did not mention such difficulties was not reassuring but rather aroused the suspicion that some of their find-ings might not be so exact as the cold finality of their figures seemed to imply. Consequently, I proposed a new way of analyzing data of this kind (May. field, 1960. The Kirtland's Warbler. Cranbrook Inst. of Sci., Bloomfield Hills, pp. 182-209). There, however, the method was incidental to the results, and it was complicated at every turn by the effect of Brown-headed Cowbirds (Molothrus ater) in the nests with the warblers. So I am offering here a sim-plified explanation for the benefit of field workers with little training in