Characteristics of Crataerina pallida (Diptera: Hippoboscidae) populations; a nest ectoparasite of the common swift, Apus apus (Aves: Apodidae)

An essential pre-requisite to understanding the nature of a host–parasite relationship is a good knowledge of the parasite’s ecology, including its life history. Despite removing a significant amount of blood from their common swift (Apus apus) hosts, no detrimental effect of parasitism by the louse fly (Crataerina pallida) has been found. This may be because little is known of the characteristics of the populations of this parasite. We studied the structure of louse fly populations that may influence its pathogenicity. High levels of prevalence were seen, with 100% of nests being parasitized during 2007 and 2008. Louse fly pupae were found to be aggregated, with a frequency distribution best described by the negative binomial model in 2006–2008. The mean parasitic load per nest was 3.72 ± 2.65 in 2007 and 4.21 ± 3.09 in 2008, much higher than that found in comparative studies. Louse fly numbers declined throughout the swift breeding season. Parasite populations were heavily female biased, except for at the initial and final stages of the nestling period.