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Publication Date

6-1-2003

Abstract

We studied the frequency and ecological correlates of intraspecific brood parasitism, physical transfer of eggs between nests, and destruction of eggs by conspecifics in colonially nesting Cave Swallows (Petrochelidon fulva) and Cliff Swallows (P. pyrrhonota) in south Texas in 2001. Brood parasitism was detected in 4.6–5.0% of Cave Swallow nests and in 10.7–11.9% of Cliff Swallow nests. Brood parasitism was not significantly related to colony size in either species, to eventual success of the host nest, to overall colony nesting success, or to date of clutch initiation. Brood parasitism was more common than expected in nests with larger clutches. Physical transfer of eggs was detected in 0.7–2.0% of nests of these species. Egg destruction by conspecifics occurred in at least 9.5% of Cave Swallow nests and 7.9% of Cliff Swallow nests. In both species, egg destruction was greatest in larger colonies. Egg destruction was unrelated to clutch size or laying date for both species. Nests with brood parasitism tended to be more likely to also suffer egg loss than nonparasitized nests in both species. Cliff Swallows apparently parasitized nests more often than Cave Swallows, but the frequencies of brood parasitism, egg transfer, and conspecific egg destruction in the two species in south Texas appeared broadly similar to those reported for Cliff Swallows in Nebraska despite geographical differences in habitat, seasonality, breeding phenology, and levels of sociality between the species. The advantages of destroying a conspecific’s eggs are unclear, but egg destruction may be a prelude to brood parasitism. The risk of losing an egg to conspecifics is a cost of coloniality for both species.

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