The breeding success of Common Swifts Apus apus is not correlated with the abundance of their Louse Fly Crataerina pallida parasites

Abstract

Capsule: Parasitism has no apparent detrimental effect. Aims: To determine whether parasitism by a haematophagous nest ectoparasite, the Louse Fly Crataerina pallida has a detrimental effect on the reproductive success of its Common Swift Apus apus hosts. Methods: An association between C. pallida abundance and various host life-history parameters indicative of host reproductive success were sought. Results: No relationship was found between measures of parasite load and clutch size, brood size, length of time required to reach nestling asymptotic weight, the length of time from hatching to fledging, fledging success per nest, fledgling weight, and fledgling size. Conclusion: Parasitism has no apparent detrimental effect upon its hosts. Louse Flies may have evolved low levels of virulence or the negative effects expected as a consequence of its parasitism may be expressed on life-history traits other than those studied here. © 2010 British Trust for Ornithology.