· From 2002 to 2004 the feeding ecology of different bird species was studied in Berlin. Thereby consequences like the success in reproduction were also examined. Beside the survey of the breeding bird (2002) and the winter bird community (2002/2003) in five study sites each covering an area of approx. 20 ha along an urban gradient, the species Blue Tit, Greenfinch, House Sparrow and Kestrel were researched in detail.

· In total, 35 breeding bird species were found in the five sites, which were characterised by different building structure, land use and vegetation cover. Considering the species` number, an urban gradient was clearly visible. In the city centre (Ze) 12 species were recorded, in the industrial area (Ge) 15, in the high-rise apartment building area (Ho) 17, in the detached family housing (Eh) 18 and in the park (Pa) 28 species. The increase in species numbers traces back to the fact that with the distance to the city centre species emerge, besides the common species, which need a diverse vegetation structure. Thus, for example the Pa offered many entomophagous birds the good conditions, which cannot be found in high-density areas. The Ge showed the lowest abundance of breeding birds with 52.4 bp/10 ha, the Eh with 96.5 bp/10 ha the highest.

· During the winter bird census a total of 3,763 individuals and 30 bird species was recorded. The lowest species number was found in the Ze (9), the highest in the Eh (20). The sum of individuals and the species number show the contrary: whereas the highest number of individuals was recorded in the urban areas, in the Ze and in the Ho, there were fewer species than in the other study sites. In the Ho, there was the highest number of anthropogenic feeding sites as well as the highest number of foraging or feeding individuals (478, all four surveys added up). It was documented in all study sites, which structures were used to which degree for foraging: the ground, the shrub layer, the tree layer or anthropogenic structures. On urban sites, like the Ho, unspecialized species like House Sparrow and Feral Pigeon benefited from the feeding by human (so-called anthropogenic structures) whereas in the Pa almost exclusively natural structures were used (especially the tree layer), like by the Nuthatch.

· The highest abundance of the predominantly insectivorous Blue Tit was recorded in the Eh (9,1 bp/10 ha). The Pa followed (8,0 bp/10 ha) thereafter, the Ze was at the last position (1,5 bp/10 ha). In especially hung-up Blue Tit-nest boxes (10 per site), there were 24 broods in 2003 (23 first broods and one second brood), 19 of these broods being successful. Considering the parameters of the breeding biology (date of first egg laying, clutch size, hatching rate and fledging success, there was no significant difference between the study sites, what, however, is mainly traced back to the small sample size. In the Pa, the highest reproduction success (5,9 fledglings/brood) was recorded, in the Ze the lowest (2,3 fledglings/brood). On the basis of the nestlings’ condition and the reproduction success, as well as by documentation of the feeding behaviour of the adult birds by means of video recording (camcorder), it became clear, that food supply was best in the Pa.

· The highest abundance of the herbivorous Greenfinch was recorded in the Eh (11.1 respectively 11.6 bp/10 ha) in 2002 and 2003, the lowest in the Pa (1.7 respectively 2.6 bp/10 ha). In total, one found 15 broods in the Pa, of which 7 were successful. With 4 successful broods the Ze was in the fore, in the Ge and in the Pa there were no fledged young at all. The explanation for this fact cannot be found in the feeding ecology of this species since predation and disturbances at the nest site are the important factors for this open cup nester. Observations of the use of certain plant species are given and discussed.

· The omnivorous House Sparrow was, considering the total abundance, the most common species in the five sites. During the breeding bird survey a total abundance of 25.8 % was documented, during the winter bird census 41%. The abundance depended on building structures and food resources of human origin: in the Ho the highest densities were recorded, in the Pa the lowest, both in summer and winter. This confirms the strong attachment of the House Sparrow to human, on the one hand as building breeding species, on the other hand concerning the availability of food. The highest reproduction success was found in the Ho, what argues for a sufficient vegetation with the availability of insects and spiders as nestling food as well.

· From 2002 to 2004, the carnivorous Kestrel was examined independent from the five study sites at ten nesting sites (nest boxes), which were located in three different zones: City (Ci), Mixed Zone (Mi) and Suburban Zone (LZ). The prey species spectrum was studied by pellets analysis and the remains of plugged feathers. There was no significant difference between the three zones with regard to the success in reproduction. In all three zones high numbers of fledged young were recorded, losses of nestlings were minor. In average there fledged 4.7 young/brood. However, in regard to the composition of food, an urban gradient was clearly visible. Thus birds were the main prey in the Ci and their proportion decreased towards the LZ. With mice and shrews it was the opposite. Striking were anthropogenic food items, like cutlet bones, found in every nest box in the Ci in all three years, which shows the adaptation to humans not only with regard to nesting sites (buildings) but also with regard to feeding ecology.

· It is being discussed, if the reproduction in the five sites of the species studied in detail suffices to sustain the populations. Considering the Blue Tit and the Greenfinch, it is assumed that immigration takes place from optimal areas to suboptimal areas. However, solely the prey species list of the Kestrel shows that Blue Tit, Greenfinch and House Sparrow get along well all in all, also in the city centre: the House Sparrow ranked first, the Greenfinch second and the Blue Tit sixth of the captured bird species.

· Recommendations for the protection and conservation of the single species are given, like growing of native trees and bushes, which offer a rich insect and spider fauna for the birds (e. g. common oak, maple, linden tree).

· Especially in a metropolis like Berlin there is need for further research, because the synurbization of different bird species progresses permanently. It is important to understand the developing mechanisms and adaptations in a city, so that one can conserve and protect the avifauna in the long run.