Michal Ferenc

A comparison of point counts with a new acoustic sampling method: a case study of a bird community from the montane forests of Mount Cameroon

Acoustic signals are frequently used for estimating avian species richness, abundance and community composition. However, sampling by traditional methods of bird surveys is often limited by availability of experienced researchers in the field, especially in the tropics. New bioacoustic approaches offer some solutions to such limitations and provide opportunities for more extensive spatial and temporal sampling. In our study, we compared results of traditional point counts with simultaneous acoustic samples obtained by automated soundscape recording units in the montane forest of Mount Cameroon. We showed that the estimates of species richness, abundance and community composition based on point counts and post-hoc laboratory listening to acoustic samples are very similar, especially for a distance limited up to 50 m. Species that were frequently missed during both point counts and listening to acoustic samples were typically those with relatively quiet songs. Abundances were rather underestimated by listening to acoustic samples in the most abundant species, including those occurring in flocks and species with low singing activity. Despite some possible biases, we demonstrated that the method based on listening to acoustic samples is relatively effective and offers a useful alternative approach for surveying Afromontane bird communities.

Geographic variation in avian clutch size and nest predation risk along a productivity gradient in South Africa

Geographic variation in avian clutch size is thought to be related to the variation in nest predation rate and food availability. We studied predation on artificial ground nests along a large-scale geographic gradient in South Africa characterised by increasing productivity from the deserts in the west to humid savannas in the east, and calculated mean clutch sizes of birds occurring in atlas quadrates surrounding our study sites. Clutch sizes generally increased with increasing productivity and seasonality. The least productive desert site was characterised also by the highest predation rate, whereas all the other sites located in savannas revealed much lower and more or less constant predation rate. We found no evidence for relationship between nest predation rates and clutch sizes of ground-nesting birds. This indicates that food availability is the major factor responsible for geographical variation in bird clutch sizes across South Africa, though high predation rate might also contribute to low clutch size in least productive arid environments.

Large-scale commonness is the best predictor of bird species presence in European cities

Urban bird communities are homogenized across large spatial scales, suggesting that the urban environment acts as an environmental filter. We hypothesize that large scale commonness is a better predictor of urban affinity of birds than any particular species trait. We estimated the relative importance of taxonomy, reproductive, ecological and morphological traits, and commonness of individual bird species. We compiled data on i) breeding bird communities of 41 European cities from urban bird atlases, and ii) regional bird assemblages defined by nine grid cells of the Atlas of European Breeding Bird around each city, and quantified the urban affinity of each species by comparing its incidence in cities and in randomly drawn communities from respective regional assemblages. Conditional inference tree-based random forest analysis was utilized to assess the importance of individual predictors. A sign test was used to detect differences between congeneric pairs of species with contrasting affinity to cities. Birds associated with woody habitats and those having altricial chicks had higher affinity for cities. Of the other reproductive traits, only clutch size showed an association with urban affinity. Different bird orders differed significantly in their urban affinity, exemplifying the homogenizing effect of cities. However, by far the most important factor associated with bird tolerance to the urban environment was species commonness, indicating that either the traits associated with commonness, or population effects driven by commonness, are responsible for their presence in cities.