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  • Author: Gábor Ónodi x
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Abstract

This study was carried out in Hungary, in an old, unmanaged, riparian poplar-willow forest, where two invasive tree species, the green ash and the boxelder maple are presented and reproduce more effectively therefore are more abundant than the native species in the study area. There are also invasive hybrid wild grapes to be found. These invasive plants cause widespread problems in floodplain forests in Central Europe. We studied Great-spotted and Lesser-spotted Woodpeckers. We investigated the following questions: Which tree species are preferred by the foraging birds? How are the foraging birds distributed spatially between the microhabitats? Are there any differences in terms of foraging niche utilization between the two studied species? We gathered our data through weekly standard observations throughout two whole years. Based on our findings we could determine that both species preferred the less abundant native trees rather than the invasive ash and maple trees, though Lesser-spotted Woodpeckers preferred hybrid wild grapes the most. Great-spotted Woodpeckers preferred the middle heights of the trees, they also moved mainly on trunks. Lesser-spotted Woodpeckers used the thinnest branches in the canopy. Based on our results we predict that the decrease of the native tree species may create a suboptimal habitat compared to the current situation. As the studied species are the major cavity excavators, the above mentioned changes will probably have significant effects on numerous cavity dependent species.

Abstract

This study was carried out in Hungary, in an old unmanaged riparian poplar-willow forest during the breeding seasons of 2014 and 2015. The occurrence of two invasive tree species, the green ash and boxelder, is significant in the study area, which influences negatively the populations of native riparian tree species in Central Europe. We studied Great-spotted Woodpecker nest sites in the presence of these invasive species. Throughout the study period, eight and twelve nesting cavity trees were mapped. Trees were recorded in 20-20 circular plots of 0.05 ha both for each mapped nest trees and random plots as well. Species, diameter at breast height and condition were recorded for each tree. Composition and diversity of nest site and random plots were compared. Distributions and preferences were calculated for nest tree use. Most of the recorded trees were invasive. Nest site plots had more native trees compared to random plots. Nest site showed higher diversity in terms of all three variables. Decayed and dead willow and white poplar hybrid trees were preferred for nesting. Diameter at breast height of nest trees was between 30-90 cm. Studies about cavity excavators in transformed habitats have high importance for nature conservation of riparian forests.

Abstract

This study was made in a postglacial relic bog in the Ócsa Protected Landscape Area in Hungary. Secondary succession of vegetation began after peat extraction and a grove-like forest evolved. Among the eight woodpecker species that occur in this area, the Great-spotted Woodpecker is the most abundant with the largest amount of data, it is for this reason we chose this species to study. The aims of this work were to detect changes in the abundance of the study species in relation to forest succession; to examine the seasonal patterns of these changes in abundance, and to identify any relationship between the height of the trees near the nets and the number of captured birds. We used the data from 1411 mist-netted Great-spotted Woodpeckers (1984- 2010), which were captured at the Ócsa Bird Ringing Station (120 standard mist nets). The assessment of forest succession rates were based on aerial photos (1979-2010). We measured the height of the vegetation, at 12 points, near each 12 m long net. Population growth of Great-spotted Woodpeckers was significantly correlated with the rate of afforestation. The majority of birds occurred only during the dispersal period. The pattern of the captures correlated well with the vegetation structure, not just with height, but also with vegetation quality as well