Stomach content and grit ingestion by Rook Corvus frugilegus nestlings

Abstract

Stomach content was examined in 53 out of 56 dead Rook Corvus frugilegus nestlings found in several breeding colonies in Poland. The stomachs contained 29 different types of items, 46.5% of which were animal, 12.2% plant and 41.2% mineral (small stones, sand and brick fragments). Imagi and larvae of Coleoptera were the most common animal prey (40% of all food items). Small stones and brick fragments were recorded in 27 (48%) chicks and their number per stomach ranged from 1 to 60 (average ± 95%CI = 9.0 ± 3.8-14.1). Statistically significant positive correlation was detected between the chick weight and the number of grit particles found in the stomach.