The kestrel (Falco tinnunculus L.) in Berlin:: investigation of breeding biology and feeding ecology

Approximately 200-250 pairs of kestrels (Falco tinnunculus) breed in Berlin, preferentially in nest boxes. From 2002 to 2004, ten monitoring sites (breeding sites) characterised by different housing structure, land utilisation, vegetation cover and degree of building density were studied in Berlin: four in the city centre, three in a mixed zone and three in the outskirts. All pairs bred in nest boxes, so the reproductive success could easily be determined. Pellets, and feathers of bird prey species, were collected during the breeding seasons, and the food spectrum was determined based on these remains. There was no significant difference in the reproductive success of the kestrels between the three zones. Data on the number of fledged young indicated a sufficient food supply. In total, 9 species of mice and shrews, 23 bird species and 31 beetle species were identified as prey of kestrels. Urban kestrels specialise in hunting birds if mice and shrews are not readily available, with the house sparrow (Passer domesticus) as the favoured prey bird. Of note are anthropogenic food items, such as cutlet bones, that were found only in the city centre. This shows that the kestrel can adapt itself to humans with regard to its diet. There was no urban gradient with regard to reproductive success, but there was with the composition of food, such as the domination of bird prey in the city centre. The number of individual items of bird prey decreased from the centre to the outskirts. In conclusion, the results show that the kestrel is an opportunistic species which survives well anywhere in the city of Berlin.