Haematocrit and blood biochemical parameters in free-living Eurasian eagle owls (Bubo bubo) from Southeastern Spain: study of age and sex differences

The study of haematocrit and biochemical parameters is considered a useful tool for diagnosis of health status in birds. However, an adequate interpretation requires reference values for each species. Moreover, factors such as age and sex should also be taken into account, as it is well known that they can also influence several parameters. For these reasons, serum biochemical parameters (albumin, calcium, phosphorus, aspartate aminotransferase, alkaline phosphatase, cholesterol, triglycerides, creatine kinase, γ-glutamyltransferase, glucose, lactate dehydrogenase, total proteins and uric acid) were studied in 15 adults (6 males and 9 females) and 258 chicks of free-living Eurasian eagle owl ( Bubo bubo ), one of the owls with the largest distribution range worldwide. Most blood clinical parameters were higher in nestlings than in adults, but only significantly for alkaline phosphatase, phosphorus and uric acid. On the contrary, γ-glutamyltransferase was significantly lower in nestlings. In adults, sex differences were not significant. Haematocrit was studied in 13 adults (2 males and 11 females) and 162 nestlings, and levels were significantly higher in adults than in nestlings. Because samples were obtained from healthy free-living individuals and the values fall within the range of levels considered physiological for similar species, we suggest that can be used as reference values for Eurasian eagle owls.