Nest site preference and nest success in blackcaps Sylvia atricapilla in Poland.

Predation is reported to be the main cause of nest failure in songbirds and selection of safer nest sites is thus an important determinant of breeding success. We studied the effect of nest site location: in bramble, elder or hornbeam, on breeding success as well as selection of different nest sites in the blackcap Sylvia atricapilla, a species whose nests are heavily preyed upon both by rodents and corvids. We found that breeding success differs between nest site types, with higher levels of predation of nests built in elder or hornbeam than of those in bramble. We also found that blackcaps select bramble when it is available within the nesting territory. Nests in bramble were better concealed than those in elder or hornbeam. Since nest height above the ground did not differ according to the plant species used, nest concealment was probably the main factor affecting blackcap nest survival.