Rhodamine-injected eggs to photographically identify small nest-predators

Photographs that clearly disclose avian-nest predators are difficult to obt ain, particularly when predators are small and exhibit subtle depredatory b ehavior. We exposed House Sparrow (Passer domesticus) eggs injected with Rh odamine B dye in camera-monitored ground nests for 12-d periods at 76 sites within mixed-hardwood forest stands in central Massachusetts, June-July 19 97. Dye-injected eggs enabled us to recognize with certainty when eggs were breached at the nest because their contents were fluorescent pink and read ily detected photographically. Eleven potential predator species were ident ified disturbing nests, of which eight were confirmed as predators. Eastern chipmunks (Tamias striatus) were the most frequent predators detected, alo ng with fisher (Martes pennanti), raccoon (Procyon lotor), Blue Jays (Cyano citta cristata), Black-capped Chickadees (Poecile atricapillus), red squirr els (Tamiasciurus hudsonicus), an Eastern Towhee (Pipilo erythrophthalmus), and a white-footed mouse (Peromyscus leucopus). White-footed mice were the most commonly detected species disturbing nests, but were photographed onl y once actually destroying an egg. The visual cue provided by dye-injected House Sparrow eggs confirmed depredatory behavior by eastern chipmunks, Bla ck-capped Chickadees, an Eastern Towhee, and a white-footed mouse.