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.
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Many authors have demonstrated use of plants and animals as sensitive biomonitors for climate changes. This research was conducted in the Mokrice area (mixed agricultural landscape and small deciduous woods) in northwestern Croatia and studies cover the period from 1979 to 2007. This paper assesses evidence that year and local air temperature changes influence first arrival dates of the migratory passerine Blackcap, Sylvia atricapilla. The mean first arrival date of the Blackcap was 2 April (1979-2007). Correlation between timing of arrivals and year was significant (P <0.001). Blackcap arrival dates have become 9.3 days earlier during the research period (slope of linear regression = -0.32 [plus or minus] 0.01). The relationship between spring temperatures (March-April) and year (P = 0.019), and spring temperatures and timing of arrival (P <0.001) was also significant. This result suggests that Blackcap respond to spring temperatures by earlier arrivalat breeding grounds.
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