Date of this Version
The Prairie Naturalist 49:23–25; 2017
Nest success rates often are higher among cavity-nesting birds than those that nest in open cups or on the ground (Martin and Li 1992, Wesołowskiand Tomiłojć 2005). Among cavity-nesting birds, woodpeckers have some of the highest rates of nest success (Johnson and Kermott 1994). A review of woodpecker nesting ecology across species documented nest success ranging from 0.42 to 1.00 with a median of 0.80 (n = 84 populations), and that predation was low, ranging from 0.00 to 0.35 with a median of 0.13 (n = 33 populations, Paclík et al. 2009). The constrained opening to a cavity nest limits predation to relatively small animals or those able to break open cavity walls (Paclík et al. 2009). Snakes can readily enter cavities, and predation by various snake species has been observed or assumed a significant cause of egg and nestling mortality for red-headed woodpeckers (Melanerpes erythrocephalus; Ingold 1991, Hudson and Bollinger 2013).
The bullsnake (Pituophis catenifer sayi), a subspecies of the gopher snake (Pituophis catenifer), is found throughout the Great Plains region of North America, parts of the Midwest, and northeastern Mexico (Conant and Collins 1998). Gopher snakes typically eat terrestrial and subterranean mammals, but a study of 2,600 preserved specimens demonstrated that 11.9% of ingested prey were bird eggs, 8.1% were birds, and 0.7% were either nestlings or bird eggs, with frequencies regionally greater in the Great Plains (Rodrigues- Robles 2002). In captivity, bullsnakes have been shown to develop an exclusive appetite for bird eggs, preferring eggs over live rodents and nestling birds (Imler 1945).