The effect of digestion on the osteological composition of owl pellets

Determinations were made, by analysiDg owl pellets, of tbe elements missing from skeletons of birds and mammals fed to three species of owls. It was found that the pelvic girdle is most often missing (up to 80 %), and less often skulls (up to 35 %) and mandibulae (maximum 25 %), due to damage and digestion of bones in the birds' stomachs. In general the largest number of missing elements of tbe skeleton occurred in the tawny owl (51 %) and long-cared owl (46 %)» and a smaller number io the barn owl (34 %). Losses in the mmiber ?f in­ dividuals identified in owl pellets were correspondingly: 16%, 20% and 8%, The amount of missing elements of the skeleton is in reverse proportion to the age of the owls and their prey. Introduction Material and methods Eesults Losses in different elements of the skeleton Losses in different elements of the skeleton depending on the age of prey Losses in number of individuals Degree of digestion of bones in different species of owls Age of owls and degree of digestion of bones Likelihood of finding birds' rings in owl pellets Discussion and conclusions References