Before breeding, hole nesting birds face the problem of the presence of old nest material from previous seasons in their nest sites. This material fills the cavity, making it shallower, resulting in greater brood vulnerability to predators, as well as creating good conditions for ectoparasite development. As a consequence, this may negatively affect many breeding parameters of hole nesters. However, adult birds may compensate the effect of blood sucking ectoparasites by increasing their feeding rates. It is known that the European Starling Sturnus vulgaris L. can deepen its nest site by removing old nest material. Therefore, a study was conducted to find out whether the presence of old nest material influences ectoparasite abundance in newly built nests, reproductive parameters, as well as nestlings’ body parameters and feeding rates in this species. An experiment with nestboxes was carried out in two forested areas. Two groups of nestboxes were prepared – one contained old nests from the previous breeding season, and the other group was cleaned with old nests removed. During the breeding season, data on Starling reproduction were collected, i.e. laying dates, clutch size and number of fledglings. Nestling body parameters were measured on the 6th, 9th, 13th and 17th days of their lives. On the 10th and 15th days of nestling life, the number of feedings was counted over a period of 30 minutes. Nests were collected and analyzed for the presence of ectoparasites. It was found that the average number of ectoparasites, both fleas and mites, was greater in nests built on old nest material, and that this number was highly correlated. In further analysis, two possible effects on reproductive output were investigated separately: the presence of old nest material and the abundance of ectoparasites. Clutch size and number of fledglings were smaller in broods from nestboxes containing old nest material, but there was no such relationship to laying dates and nestlings’ body parameters (weight, tarsus and wing length). The number of feeding trips on the 10th day of nestling life was higher in “cleaned” nestboxes, but a similar level was achieved by the 15th day in both groups of nestboxes. It was found that ectoparasite abundance did not influence any of the studied parameters of Starling reproduction, i.e. breeding, nestlings’ physical condition or number of feedings. This confirmed earlier findings that ectoparasite infestation at a natural level does not affect Starlings’ breeding. It seems that the negative effect of the presence of old nest material in nest sites is connected to the costs of site preparation and old nest material removal, which are borne by the females.
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