SummaryThe biodiversity and naturalness of forests that cover stream valleys in submontane areas have not been investigated as intensively as riparian forests along large lowland rivers. In this study we compared data on total bird assemblages and on selected indicator species detected in forests along submontane stream valleys (‘Vall’) with those detected in forests covering submontane slopes and tops in the foothills (‘Hill’) of the Western Carpathians, considering also environmental characteristics of the studied locations. The aim of this study was to verify the hypothesis that forests along submontane stream valleys harbour significantly richer and more diverse bird communities and that they are an important habitat for rare and threatened species. We found that the species richness, abundance of birds and bird diversity were almost twice as high in ‘Vall’ than in ‘Hill’ locations and that indicator species mostly or exclusively inhabit ‘Vall’ locations. Moreover, species diversity was highly and positively correlated with higher tree species diversity and a higher amount of large trees and dead wood, but negatively correlated with logging intensity. The results of our study confirmed that forested river valleys in submontane areas play an important role as refugia both for rare and endangered bird species as well as for the whole bird assemblage. This study is the first to present an assessment of this type of habitat for birds in the Western Carpathians. Forests along submontane stream valleys, if protected or unmanaged, could be treated as reference areas for nature and biodiversity conservation.
Several methods of sampling are commonly used to detect freshwater crayfish (Decapoda: Malacostraca). Many of them are laborious, time-consuming, and require dedicated equipment. The aims of this contribution are i) to compare visual encounter surveys and baited trap success in the detection of the noble crayfish, Astacus astacus (L.), which is endangered in Poland, and ii) to assess the time needed to detect the invasive spiny-cheek crayfish, Orconectes limosus (Raf.). The study is based on data collected between 2016–2018 in various habitats of Astacus astacus and Orconectes limosus in Poland. Visual encounter surveys are at least as effective in assessing the presence of A. astacus as the trapping method. The modal value for the detection time of O. limosus at all sites and all surveys was two minutes. Sample rarefaction showed that one survey covered 11.33 (SD = 0.43) of a maximum of 12 detections per survey. This suggests that, despite some limitations, visual detection might be an efficient method for determining crayfish presence/absence for a wide range of applications.
Aim This study investigated whether habitat fragmentation at the landscape level influences patch occupancy and abundance of the black-headed gull, Chroicocephalus ridibundus, and whether the response of the species to environmental factors is consistent across replicated landscape plots.Location Water bodies (habitat patches) in southern Poland.Methods Surveys were conducted in two landscape types (four plots in each):(1) more-fragmented landscape, in which habitat patches were small (mean size 2.2-6.2 ha) and far apart (mean distance 2.5-3.1 km); and (2) less-fragmented landscape, in which habitat patches were large (mean size 9.2-16.5 ha) and separated by short distances (mean 0.9-1.4 km). Observations were performed twice in 284 potential habitat patches during the 2007 breeding season.Results Colonies were significantly more frequent and larger in the lessfragmented landscapes than in the more-fragmented ones. Probability of patch occupancy and number of breeding birds were positively related with patch size and these relationships were especially strong in the more-fragmented landscapes. In the less-fragmented landscapes, the occurrence of black-headed gulls was negatively related to the distance to the nearest local population, but in the morefragmented landscapes such a relationship was not detected. As distance to the nearest habitat patch increased, the probability of the patch occupancy decreased in the more-fragmented landscapes. Moreover, abundance was negatively influenced by distance to the nearest habitat patch, especially strongly in morefragmented landscapes. Proximity of corridors (rivers) positively influenced the occupation of patches regardless of landscape type. The number of islets positively influenced occupancy and abundance of local populations, and this relationship was stronger in the more-fragmented landscapes.Main conclusions Our results are in agreement with predictions from metapopulation theory and are the first evidence that populations of blackheaded gulls may have a metapopulation structure. However, patch occupancy and abundance were differentially affected by explanatory variables in the morefragmented landscapes than in the less-fragmented ones. This implies that it is impossible to derive, a priori, predictions about presence/abundance patterns based on only a single landscape.
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