Abstract
Grassland birds have experienced greater population declines than any other group of birds monitored by the North American Breeding Bird Survey. Our goal was to compare demographic rates among years within species and among species of grassland birds. Eight-hundred and eleven nests of Henslow's Sparrows (Ammodramus henslowii), Grasshopper Sparrows (A. savannarum), Field Sparrows (Spizella pusilla), Dickcissels (Spiza americana), and Eastern Meadowlarks (Sturnella magna) were monitored between 1999 and 2003. Mayfield nest success including the egg-laying stage, as well as the incubation and nestling periods, was 20, 34, 15, 20, and 18%, respectively. Most nest failures were attributed to predation. Nest parasitism by Brown-headed Cowbirds (Molothrus ater) was infrequent (<2% of all nests parasitized). Clutch size decreased during the nesting season for Dickcissels, Grasshopper Sparrows, and Field Sparrows. Nesting phenology suggests the possibility of multiple-brooding for all five species in this study.
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