Evaluating prey preferences of an insectivorous bird species based on different sampling methods

Abstract

Decline in populations of farmland and grassland birds has been attributed to the recent changes of
agricultural practice in Europe. These changes may affect the food resources, so the studies in prey
preference may have an importance when try to protect these species. We studied prey preference in the
European Roller (Coracias garrulous) in natural grassland and farmland mosaics by two different sampling
methods. (i) Pitfall traps were used to determine prey availability in Rollers’ territories and (ii) nestbox
content, supplemented with video recordings, were used to estimate the contribution of main prey taxa to
nestling diet. We found that Rollers did not select their prey items in proportion to their availability. We also
found significant differences between Savage selectivity indices obtained by the different sampling methods.
Nestbox content indicated high preference of coleopterans and avoidance of orthopterans, but video
recording showed significant preference of both taxa. None of our sampling methods indicated difference in
prey preference during the nestling period between the two study sites.