Effects of physical environmental variables on the behaviour of mountain woodland songbirds

Background: The behaviour of songbirds depends on several physical environmental factors that may change with increasing elevation. For example, temperature decreases and the vegetation period is shorter at higher elevations. Birds may need to adapt to changes in environmental conditions by changing their breeding or singing behaviour. This thesis aims to contribute to understand the effects of physical environmental variables on the behaviour of mountain woodland songbirds.
Location: Switzerland, Swiss National Park
Methods: To investigate the singing behaviour of mountain woodland songbirds (Alpine tit, coal tit, Eurasian chaffinch, song thrush, mistle thrush and ring ouzel) we used passive acoustic monitoring and observations in the field. We also used citizen science data to examine changes in breeding phenology along an elevational gradient.
Results and main conclusions: We observed species-specific differences in the singing behaviour according to the investigated variables, and found only small differences in the timing of breeding between higher and lower elevations independent of climatic conditions. The effect of anthropogenic noise seemed to be context- but not species-specific, since all investigated songbird species changed their singing behaviour in noisier areas and during nosier times. Physical environmental variables, like moon phase, temperature, cloud cover or aspect, had consistent but small effects on all investigated songbird species. The effects of elevation and date, in contrast, were more species-specific. Further, alpine songbirds seem to have evolved adaptations to cope with harsher environmental conditions at higher elevations, since the investigated species were only raised with a relatively small delay at higher compared to lower elevations.