Only Some Ectoparasite Populations are Affected by Nest Re-Use: an Experimental Study on Pied Flycatchers

Abstract

Nest re-use in birds is rare but since appropriate cavities may be scarce, cavity-nesting birds may often re-use those that were occupied in previous seasons. Old nest material may contain and/or attract more ectoparasites than fresh material. Therefore it is important to understand the effects of nest re-use on the abundance of different ectoparasite species of different virulence and their impli cation for breeding parameters and nestling condition. We studied the consequences of nest re-use in a population of pied flycatchers Ficedula hypoleuca breeding in central Spain by offering them both nest-boxes with old nest material and cleaned nest-boxes. We monitored breeding activity from the early stages of nest construction until fledging, and then finally removed nests to estimate ectoparasite abun dances. Occupation rates were similar for both treatments. We found that blowfly and flea abundances were significantly higher in old nests than in new nests, but the abundance of mites, the most virulent ectoparasites on our host study population, was not affected by the presence of old nest material. Nestling growth with respect to tarsus length and mass was not affected by nest re-use although wing length was marginally and significantly reduced by nest re-use. There was no association between ectoparasite abundance and nestling growth and condition. These results question the generality of assumed higher infestations in re-used nests, on which a certain critique of nest-box studies has been based.