Success and predation of bird nests in grasslands at Valley Forge National Historical Park

Populations of grassland birds are declining in the Northeast due to habitat loss and fragmentation. Fragmentation of grasslands can contribute to lower breeding success of grassland birds by altering local predator communities. Using miniature video cameras, I estimated nest sucess an indentified nest predotors in grassland fragments at Valley Forge National Historical Park in southeastern Pennsylvania. Estimated nest-success probability for Sturnella magna (Eastern Meadowlark) at Valley Froge was 0.25 (0.04-0.65, n = 7) and similar to estimates from the Midwest, but slightly lower than other studies in the Northeast. Nest success for Spizella pusilla (Field Sparrow; 0.77 [0.31-0.98, n = 8]) and Agelaius phoeniceus (Red-winged Blackbird; 0.48 [0.18-0.80, n = 10]) was higher than estimates from other studies. The local predator community identified at Valley Forge was less diverse than documented in other studies, with only 4 species depredating 8 of 25 monitored nests. The primary predator was Odocoileus virginianus (White-tailed Deer; 38% of nest predation events) followed by Vulpes vulpes (Red Fox; 25%); Procyon lotor (Raccoon; 13%), and a probable Mustela sp. (weasel; 13%). I never detected nest predation by small mammals or snakes, which are important nest predators in the Midwest. The impact of White-tailed Deer on grassland birds at Valley Forge is uncertain, therfore further research is needed to fully understand local predator-prey community dynamics.