Ectoparasitism as a Cost of Coloniality in Cliff Swallows (Hirundo Pyrrhonota)

Abstract

Abstract. Colonially nesting Cliff Swallows (Passeriformes: Hirundo pyrrhonota) in southwestern Nebraska, USA, are commonly parasitized by hematophagous swallow bugs (Hemiptera: Cimicidae: Oeciacus vicarius) and fleas (Siphonaptera: Ceratophyllidae: Ceratophyllus celsus). We examined to what degree these ectoparasites represent a cost of coloniality for Cliff Swallows. The number of swallow bugs per nest increased significantly with Cliff Swallow colony size. Body mass of nestling swallows at 10 d of age declined significantly as the number of bugs per nestling increased. By fumigating half of the nests in some colonies, killing the bugs, and leaving half of the nests as nonfumigated controls, we showed that swallow bugs lower nestling body mass and nestling survivorship in large Cliff Swallow colonies but not in small ones. Bugs cost nestlings, on average, up to 3.4 g in body mass, and reduced survivorship by up to 50%. Parasitism by fleas showed no consistent relationship with colony size during the nestling period but increased significantly with colony size early in the season, when birds were first arriving in the study area. Fleas did not affect nestling body mass or survivorship and thus, unlike swallow bugs, are probably not important costs of coloniality to Cliff Swallows. Field observations and nest fumigation experiments showed that Cliff Swallows apparently assess which nests are heavily infested with swallow bugs early each spring and select parasite-free nests, leading sometimes to alternate-year colony site usage. Cliff Swallows were more likely to construct new nests (rather than reusing old ones) in large colonies than in small colonies, probably in response to heavier infestations of ectoparasites in the existing nests of large colonies.

Arbovirus infection increases with group size

“…Thus, the size of a cli¡ swallow colony can be considered a relative index of the bug population size at a site. This result is consistent with other analyses showing higher levels of per capita swallow bug parasitism of cli¡ swallows in larger colonies (Brown & Brown 1986, 1996.…”

Effect of Old Nest Material on Nest Site Selection and Breeding Parameters in Secondary Hole Nesters — a Review

“…However, several other studies demonstrated that ectoparasite abundance did not differ between nests built in sites with or without an old nest (Table 4). Apart from this, birds themselves may be evaluating the level of infestation, and avoiding nest sites with a high abundance of ectoparasites (du Feu 1982, Brown & Brown 1986, Loye & Carroll 1991. Thus, the costs of breeding on old nest material as it relates to the presence of ectoparasites would be not so high and controlled by birds.…”

Parasites and Social Behavior of Island Feral Horses

“…Moreover, for social serves to reduce an individual's level of harrassment, a animals the likelihood of parasite and disease transmis-benefit that also accrues to horses living in large groups sion is thought to automatically increase by living in (Duncan and Vigne 1979). And although social groomgroups (Alexander 1974, Hoogland 1979, Brown 1985, ing among primates and ungulates acts to cement many Accepted 16 January 1989 0 OIKOS types of social relationships, it serves, and probably evolved, to facilitate the removal of ectoparasites (Seyfarth 1983, Hausfater 1985. Even the ingestion of endoparasites by ungulates can be reduced by grazing in areas far from those used repeatedly by the group for defecating (Miller 1953).…”