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High flea (Siphonaptera) loads are typically found in birds' nests in nest boxes. Ten years of observations, involving Marsh Tit Paruspalustris, Great Tit Parus major and Blue Tit Parus caeruleus nests in tree cavities in primeval forests of Bialowieza National Park, Eastern Poland, demonstrated that the prevalence of fleas was below 10% of nests and that the intensity of flea infestation was low. Low flea loads may be typical for nests in tree cavities. Therefore, nest-box data about flea-host interactions should not be treated as representative for conditions in natural cavities.
1. Introduction
Fleas (Siphonaptera) constitute a substantial problem for birds nesting in nest boxes. Often over 80% of nests are infested and a nest may host several hundred fleas (Tripet & Richner 1997). Most data show negative effects of high flea loads on the reproductive performance of birds, and on the condition of nestlings and/or adults (Tripet & Richner 1997, 1999, Mazgajski et al. 1997, Tripet et al 2002, Slomczyhskia/. 2006,Tomasa/. 2007). It is postulated that, in order to avoid or to reduce the costs of flea infestation, birds have evolved several anti-flea adaptations, such as an avoidance of infested nest boxes (Rytkonen et al. 1998, CTBrien & Dawson 2005), a shiftin breeding seasons (Oppliger et al. 1994), nest sanitation (Christe et al. 1996), usage of aromatic plants as repellents (Gwinner et al. 2000, Petit et al. 2002) and modifications of parental provisioning (Tripet & Richner 1997, Bouslama et al. 2001; Tripet et al. 2002).
Importantly, all the above mechanisms of flea avoidance have been tested using nest-box-breeding bird populations. Nest boxes are a relatively recent human-introduced resource, which differ from natural tree cavities in several respects, such as microclimate and safety (Wesolowski 2000, Wesolowski etal. 2002, Wesolowski & Tomialojc 2005, Mazgajski 2007a). A reasonable question, therefore, is whether data collected from nest boxes can be generalised to natural cavities, whether the documented high flea loads are characteristic of nests in cavities in general, or whether the phenomenon of high flea loads concerns only nest boxes. There is a scarcity of data on natural cavities, but both the prevalence and intensity of flea infestation in nests in tree cavities may be negligible (Pung etal. 2000, Wesolowski & Stahska 2001). However, as these two...