Summary

Since 1976 the Kestrel (Falco Tinnunculus) has been studied in the City of Berlin/Germany. From 1985 onwards 50 km² in SW-Berlin were monitored (see KOSTRZEWA & KOSTRZEWA 1993), since 1991 the monitoring area (No. 376 in the Monitoring Raptors and Owls in Europe) measures 480 km² and includes the western districts of Berlin; 72 % are urban areas, 16 % are covered by forests, 7 % by lakes and rivers and 5 % are used for different purposes. From 1974 until 1998 174 nestboxes have been installed mainly in public buildings.

Since 1991 we also tried to find every natural breeding place, in 1998 108 such places were known in the study area. The number of territorial pairs increased considerably from 100-110 in 1991 to 150-160 in 1994 and`95, in 1996 the population dropped to 120-130 pairs and has remained stable since then. From 234 breeding attempts in nestboxes 1976-98 1786 young fledged, i.e. 4.3 young per breeding attempt, hence breeding attempts on natural places 711 young fledged i.e. 3.0 young per breeding attempt, hence breeding attempts in nest boxes were more succesful than breeding attempts at natural breeding places. First eggs were laid on the 26th March, the last clutch was begun on the 4th of July, 78 % of all clutches were laid between the 15th of April and 15th of May (n = 474). In 392 cases (380 in nest boxes, 12 in natural places) we were able to survey the complete breeding attempt from egg laying to fledging. In these 392 cases 1999 eggs were laid, 1712 young hatched (85,6 % of eggs) and 1619 young fledged (94,6 % of all young). The corresponding numbers are 5.1 eggs, 4.3 hatched young and 4.1 fledged young per breeding attempt.
Despite a large proportion of avian prey at many breeding places, the mean number of fledged young per breeding attempt varied considerably from year to year probably following ciyclic changes in vole (Microtus spec.) abundance. Good years were 1992 with 4.2 (n = 34) and 1998 with 4.4 (n = 92) young per breeding attempt, bad years were 1994 - 1997 with 3.4 young per breeding attempt in both years (n = 71 and 72).