The study covered 5 species occupying nest-boxes in urban parks most frequently: Passer montanus, P. domesticus, Sturnus vulgaris, Parus major and P. caeruleus. The main objective of the study was to find out whether nest-boxes in the conditions peculiar to urban parks enabled these species to breed successfully there. The assessment was based on a comparison of these results with those, given in the literature, from farmland and woodland near the two cities. This project is part of a wider programme of studies into the use of nest-boxes in parks in Warsaw and Poznań (Luniak 1992). Methods. Small and medium-sized nest-boxes were used in this study - wooden ones in Warsaw, sawdust-concrete ones in Poznań. Some of the material (Tab. 1) was collected while other studies were being conducted. These required frequent and lengthy nest inspections which exposed the parent birds to considerable stress. The following terms and means of calculating breeding parameters are used: „Fledged pulli" - successfully reared nestlings. Means of „Hatched pulli" and „Fledged pulli" were calculated with respect to the number of broods with cluthes. Brood losses refer to the loss of whole cluthes or all the nestlings in the nest. Productivity (pull./nest/year) was calculated as the sum of fledglings from all broods referred to the number of nests (pairs) with first and delayed clutches. Study areas. In both cities the studies were carried out in parks within the highly urbanized zone. In Warsaw, the bulk of the material on Passer montanus and P. domesticus was collected in 3 parks (Table 1), the remainder in over a dozen others. In Poznań, the study covered 2 parks. In all the parks there was quite a wide variety of predators and species destroying broods - domestic cats, Martes spp., Sciurus vulgaris, Strixaluco, Corvus monedula and Pica pica. With the exception of one area in Poznań (Ogród Dendrologiczny - Tree Garden), visited by large numbers of people. Breeding results. Table 2 compares the breeding parameters of the 5 species studied in the parks with those given in the literature for the farmland and woodland near Warsaw and Poznań. Tables 3-7 give the detailed breeding results for the 4 species in the parks. Conclusions. - The results of breeding in nest-boxes in Warsaw and Poznań parks were within the ranges typical for the species in question. - In none of the 5 species were the breeding results (clutch size, productivity) in the parks distinctly worse than those reported in the literature for nearby non-urban areas. The productivities of Passer montanus and Sturnus vulgaris in Poznań were slightly lower than those outside the city; that of Parus major in Poznań was higher. - No significant differences in breeding results between the two cities were found, and there were no regular differences, as well, between breeding results in wooden boxes (used in Warsaw) and sawdust-concrete ones (used in Poznań). - Breeding results were not visibly affected by direct human interference, the presence of large numbers of people near the nest-boxes, predation by raptors and nest robbers or interspecific competition. But the domination of Sturnus vulgaris and Passer montanus (and probably P. domesticus as well) limited possibilities of occupying boxes by Parus major and P. caeruleus. Site and intrapopulational factors were probably more important as regards limitation of productivity. - The frequent and lenghty nest inspections more often led to the loss of entire clutches/broods.
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