Effects of urbanization on nest site selection and nesting success of the Greenfinch Carduelis chloris in Krotoszyn, Poland

Abstract

Nest success was studied in relation to nest-height and urban gradient at 313 Greenfinch nests in Krotoszyn (western Poland). The nests were grouped according to three height-categories : low (< h 3.5 m). The three sites were selected to represent different intensities of human development (low, medium and high). Nesting success estimated by Mayfield and the `traditional' method was highest in the height-interval above 3.5 metres. The probability of nest survival was 37% and 39% in low and medium nests and 82% in high nests. The daily survival rate of low and medium nests was significantly lower than in high nests. This preference could serve the nests to evade mammalian predators, most probably domestic cats . Nest success estimated across an urban gradient was higher in the site of high intensity human development than in other sites. The differences estimated using the `traditional' method were significant. However, the daily survival rate between these three sites was non-significant. There were more nests than expected in the site of high intensity human development, and less than expected in the site of lower intensity urban gradient. These data confirm the `safe zones' hypothesis that as the intensity of urbanization increases the frequency of predation decreases.