The effect of nesting habitat on reproductive output of the Barn Swallow (Hirundo rustica). A comparative study of populations from atypical and typical nesting habitats in western Poland

The aim of this study was to discover if atypical nesting places such as abandoned second world war bomb shelters and conditions occurring within, can constitute suitable and good quality alternative habitat for the Barn Swallow. To answer this question, the time of breeding, clutch size and the mean survival probability of nest contents were compared between swallows nesting in shelters and in farm outbuildings - typical nesting habitat. The study showed that bunkers do constitute a suitable and relatively good quality alternative habitat for the Barn Swallow but they are poorer nesting places than pigsties or cowsheds. Mean survival rate of nest contents (eggs/nestlings) was higher in farm outbuildings than in bunkers, but only differences in the first broods were recorded. The results are most probably the effect of different conditions occurring in the two kinds of nesting habitat, especially at the beginning of the breeding season, when the unfavourable weather conditions can negatively influence breeding swallows to a higher degree in bunkers than in outbuildings.