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The influence of nest placement on breeding success of the Blackcap (Sylvia atricapilla L.) in two different forest habitats

Zieliński J.

Polish Journal of Ecology

2011

Vol. 59, nr 2

391-401

One of the hypotheses to explain a lack of relationship between nest location and breeding success of passerine birds predicts that in an environment characterized by a high diversity of predators that use a variety of foraging strategies, clutches in different locations and degrees of concealment may be equally subject to destruction. In this study I assumed that the impact of nest location on breeding success of the Blackcap Sylvia atricapilla would differ in habitats characterized by significantly different species richness and, consequently, population density and species diversity of potential predators. Thus, I expected that the influence of the nest location and particularly its concealment on breeding success of the Blackcap would be more significant in a habitat characterized by the overall low biotic diversity and low vegetation density. The study was conducted in two forested areas located in central Poland - managed pine forest characterized by low biodiversity and vegetation density and floodplain forest consisting of much higher biodiversity and having higher stand density. I assessed the influence of Blackcap nest placement (concealment, height above the ground, nest plant height, distance from the nest to the closest edge of the nest plant) on breeding success. Among the analyzed parameters, only nest concealment had a significant impact on breeding success. This conclusion, however, pertains only to the pine forest, where successful nests were better concealed than nests with clutch losses. Similar relationships were found in the floodplain forest area, but they were not statistically significant.

Forest fragment size affects edge effect in nest predation . experiment with artificial nests

Mazgajski T., Rejt Ł.

Polish Journal of Ecology

2005

Vol. 53, nr 2

233-242

Many species react negatively to forest fragmentation. If this process also decreases the abundance of forest predators we expect that birds. broods in small forest patches would be preyed upon only by predators that penetrate from the matrix while broods in larger patches would be also attacked by predators specifically associated with forests. We tested the hypothesis that an increase in forest patch size leads to an increase in predator pressure on nests. Studies were conducted in Central Poland, in an agriculturally dominant area with 6% forest cover and highly fragmented woodlot. Three patch sizes were chosen for the experiment: small (< 20 ha), medium (30 - 50 ha) and large (> 120 ha). One quail egg was placed in each nest. All transects were checked after 13 - 14 days. The highest predation level was found in medium-sized patches, the lowest . in the largest patches. We found a reverse edge effect on nest predation in the largest patches, i.e. a decreased predation risk closer to the forest/matrix border. When comparing our results with other studies, it seems that the manner of classifying forest size significantly affects the results obtained. This may explain the differences in the results of many authors studying this phenomenon.