The Breeding Ecology of the GreenfinchCarduelis chlorisin Urban Conditions (Study in Krotoszyn, W Poland)

Data were collected in a medium-sized town. During five years 342 nests were found. The densities of breeding pairs varied over this period between 4.5 and 5.9 p/10 ha. The distribution of breeding pairs was uneven throughout the study area. The preferred nest sites were the roadside trees, where 88.9% of the nests were built. The mean onset of egg-laying was 22 April (range 19–26 April). There was a tendency to start breeding earlier in warmer springs. The mean clutch size was 5.07 ± 0.74. There was a positive correlation between clutch size and the date of egg-laying. These data suggest that there was a compromise between the tendency towards earlier breeding and clutch size. In the study area the Greenfinch is a double-brooded species. Unlike other studies it was noted that the average clutch size increased in the second half of the breeding season. The maximum clutch size coincides with the second or replacement clutches. Hatching, fledging and breeding success were lowest when clutch sizes were largest. The nesting success estimated with the Mayfield and the “traditional” method was approximately similar (0.40 and 0.44 respectively). Cats and mustelids were probably the cause of most breeding failures. Corvids were not responsible for nesting failures.