We studied the nesting ecology of Swainson's Warblers (Limnothylpis swainsonii) in Britton's Neck, South Carolina, USA and found 144 nests of which 78 were active. Nest initiations followed a bimodal distribution. Clutches averaged (± SE) 3.19 ± 0.20 eggs and 2.50 ± 0.33 fledglings per nest. The Mayfield nest success estimate for a 23-day cycle was 50%. Logistic exposure models indicate nest success to be most impacted by Brown-headed Cowbird (Molothrus ater) nest parasitism, nest age, and distance to the nearest swamp. Unparasitized nests that were younger in age and further from a swamp had the highest daily survival rates. Ten percent of nests were parasitized by Brown-headed Cowbirds with a 26% reduction in Swainson's Warbler hatching and an 89% reduction in fledgling production. Multiple brooding was observed in 21% of 2000 and 2001 Swainson's Warbler nests. Vines, such as greenbrier (Smilax spp.), were the most common substrate used for nesting, although two-thirds of the nests contained cane (Arundinaria tecta and A. gigantea) within a 5-m radius.

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