Structure and composition of prey remains of Cinereous Vultures (Aegypius monachus) from an adaptation aviary in Bulgaria

This article presents the results of a study on the shape and composition of Cinereous vulture ( Aegypius monachus ) pellets. A total of 501 pellets were collected during two different seasons – 125 on 24 September 2025 and 376 on 10 March 2025. The birds from which the materials were collected were raised in a closed adaptation aviary near the town of Madzharovo and were fed with the carcasses of various domestic animals - Karakachan sheep ( Ovis aries ), horses ( Equus ferus caballus ), Native Bulgarian goat ( Capra hircus ), Shorthorn Rhodopian Cattle ( Bos taurus ), Bulgarian Gray Cattle, Bulgarian Black and White Cattle, European Bison ( Bison bonasus ) and domestic pigs ( Sus domesticus ). The study reveals the shape and composition of each of the pellets during the two collection periods and the results aim to highlight the similarity between them and the existence of a common type of pellet for the Cinereous vulture. This study also aims to determine what part of the food composition remains in the pellet after the carcass has been processed. After analysis, two types of residue were found in them - nutritional and non-nutritional. The nutritional residues consisted of fur and skin - as the highest percentage, stomach contents, bones, hooves, horns and feathers from vultures, while the non-nutritional residues consisted mainly of stones and sticks - as the most significant percentage, leaves, construction foam and plastic (sisal and cord).