Bone composition and bone mineral density of long bones of free-living raptors

Bone composition and bone mineral density (BMD) of long bones of two raptor and one owl species were assessed. Right humerus and tibiotarsus of 40 common buzzards, 13 white-tailed sea eagles and 9 barn owls were analyzed. Statistical analysis was performed for influence of species, age, gender and nutritional status. The BMD ranged from 1.8 g/cm3 (common buzzards) to 2.0 g/cm3 (white-tailed sea eagles). Dry matter was 87.0% (buzzards) to 89.5% (sea eagles). Percentage of bone ash was lower in sea eagles than in buzzards and owls. Content of crude fat was lower than 2% of the dry matter in all bones. In humeri lower calcium values (220 g/kg fat free dry matter) were detected in sea eagles than in barn owls (246 g/kg), in tibiotarsi no species differences were observed. Phosphorus levels were lowest in sea eagles (humeri 104 g/kg fat free dry matter, tibiotarsi 102 g/kg) and highest in barn owls. Calcium-phosphorus ratio was about 2:1 in all species. Magnesium content was lower in sea eagles (humeri 2590 mg/kg fat free dry matter, tibiotarsi 2510 mg/kg) than in buzzards and owls. Bones of barn owls contained more copper (humeri 8.7 mg/kg fat free dry matter, tibiotarsi 12.7 mg/kg) than in the Accipitridae. Zinc content was highest in sea eagles (humeri 278 mg/kg fat free dry matter, tibiotarsi 273 mg/kg) and lowest in barn owls (humeri 185 mg/kg, tibiotarsi 199 mg/kg). The present study shows that bone characteristics can be considered as species specific in raptors.