Grazing by large herbivores is increasingly used as a management tool in European nature reserves. The aim is usually to support an open but heterogeneous habitat and its corresponding plant and animal communities. Previous studies showed that birds may profit from grazing but that the effect varies among bird species. Such studies often compared bird counts among grazed areas with different stocking rates of herbivores. Here, we investigated how space use of Konik horses and Highland cattle is related to bird counts in a recently restored conservation area with a year-round natural grazing management. We equipped five horses and five cattle with GPS collars and correlated the density of their GPS positions on the grazed area with the density of bird observations from winter through the breeding season. We found that in the songbirds of our study site, both the overall density of bird individuals and the number of species increased with increasing density of GPS positions of grazers. Correlations of bird density with horse density were similar to correlations with cattle density. Of the eight most common songbird species observed in our study area, the Eurasian Skylark and the Common Starling had the clearest positive correlations with grazer density, while the Blackbird showed a negative correlation. Skylarks and Starlings in our study area thus seem to profit from year-round natural grazing by a mixed group of horses and cattle.

No abstract

In birds, observed adult sex ratios often are biased towards males. This bias could arise due to differences between sexes in dispersal or in detectability / catchability, but a preferred explanation has been sex differences in survival. However, most studies investigated apparent survival, in which differences in dispersal were not accounted for. Here, we used data from 24'830 capturesof 11 bird species, collected at 40 Hungarian constant effort ringing sites, to estimate true survival, dispersal, and capture probability. On average, dispersal and capture probabilities were similar between sexes. However, the probability to survive from one year to the next was 0.46 in males but only 0.37 in females, suggesting that higher female mortality may indeed be the most important predictor of male-biased adult sex ratios.

Context Grazing by large herbivores is an increasingly used management tool in European nature reserves. A challenge in grassland conservation is to maintain both the openness and the heterogeneity of the habitat, to support their animal communities, including birds. Horses and cattle are often used to create and maintain patchy landscapes, especially in rewilding projects, but the influence of grazers on birds is often debated by conservationists.Objectives We studied how the abundance and species richness of birds of four foraging guilds are related to the area use of Highland cattle and Konik horses in an alluvial grassland. We also investigated how season and landcover influences the spatial distribution of individuals and species of different bird guilds on the grazed area.Methods We equipped all grazers with GPS-collars to assess the density of their hourly positions. We made weekly transect counts of birds to describe their distribution, and carried out landcover surveys to describe the habitat. We used GAMM models in a spatially explicit framework.Results Open-area foraging birds were clearly associated with higher grazer densities, and aerial, wetland and woodland birds also seemed to profit from low-intensity year-round grazing. Most bird species and individuals were observed on open landscapes scattered with woody patches and waterbodies, and at areas with moderate grazer density. The number of birds on the grazed area was about twice as on the ungrazed control area.Conclusions A heterogenous landscape maintained by low-intensity grazing seems to fulfil the needs of birds with different feeding ecologies.

In birds, observed adult sex ratios often are biased towards males. This bias could arise due to differences between sexes in dispersal or in detectability / catchability, but a preferred explanation has been sex differences in survival. However, most studies investigated apparent survival, in which differences in dispersal were not accounted for. Here, we used data from 24'830 captures of 11 bird species, collected at 40 Hungarian constant effort ringing sites, to estimate true survival, dispersal, and capture probability. On average, dispersal and capture probabilities were similar between sexes. However, the probability to survive from one year to the next was 0.46 in males but only 0.37 in females, suggesting that higher female mortality may indeed be the most important predictor of male-biased adult sex ratios.