Responses of Barn Swallows to Eggs, Young, Nests, and Nest Sites

Abstract

Aspects of egg, young, nest and nest site recognition have been investigated or observed in several species of birds (e.g., Cullen 1957, Davies and Carrick 1962, Beer 1969, Peek et al. 1972). In general, selection appears to favor recognition of as few characteristics as necessary to insure a high probability of caring for the correct eggs or young. Birds that build nests respond to their nest sites, and later their young (usually when mobile), but show little evidence of specifically recognizing their own nests or eggs (Nice 1943, Tinbergen 1953, Beer 1970). Common Murres (Uria aalge; Johnson 1941, Tschanz 1959), which do not build nests, and Royal Terns (Sterna maxima; Buckley and Buckley 1972), which nest in dense colonies where their eggs may be displaced, recognize both their eggs and laying sites. Among passerines, Rothstein (1975) found that some species (rejector species) can recognize foreign eggs placed in their nests, while others (acceptor species) do not. Bank Swallows (Riparia riparia; Hoogland and Sherman 1976), Red-winged Blackbirds (Agelaius phoeniceus; Peek et al. 1972), and Carrion Crows (Corvus corone; Yom-Tov 1976) do not discern their eggs, or their young until near fledging, at an age when an error in progeny care is possible. Tricolored Blackbirds (Agelaius tricolor), which nest in dense colonies, accept eggs or young placed in their nests (Emlen 1941). Many non-passerines are similar in their varied ability to recognize their eggs or young (Tinbergen 1953, Davies and Carrick 1962, Beer 1970). Red-winged Blackbirds recognize their nest sites specifically, but accept substitute nests (Peek et al. 1972). Nero and Emlen (1951) found that female Red-winged Blackbirds would follow displaced nests even across territorial boundaries of males. Meise (1933) moved the nest of a House Sparrow (Passer domesticus) 1.5 m and observed no response to it by the adults. Among non-passerines, a Cooper's Hawk (Accipiter cooperii) nest moved in small increments from its original location in the crotch of a tall tree to a bushel basket, and then to the ground, was accepted at each step by the adults (Allen 1951). Herring Gull (Larus arg ntatus) nests moved about 30 cm were accepted if they contained eggs and the original nest site was covered with sand (Tinbergen 1953). In experiments with Sooty Terns (Sterna fuscata), birds returned to their nest sites rather than to nests displaced short distances (Lashley 1915). From these studies, it appears that selection favors more rigid responses to changes in nest and nest site for colonial than for non-colonial species. In the present study, I evaluated responses of Barn Swallows (Hirundo rustica) to their eggs, young, nests, and nest sites. Barn Swallows are facultative colonial nesters and unique among the above species in that their colonies are passive aggregations of birds (Snapp 1976). Barn Swallows have recently used man-made structures for nesting (Bent 1942), and such behavior may influence the size of their aggregations. Do swallows respond to aspects of the nesting situation in the same way as colonial or noncolonial species?