Haematological and biochemical reference values for Bonelli's eagles in the wild and in captivity: implications for conservation and rehabilitation programs

Abstract

Background Haematological and clinical biochemistry analyses are essential tools for evaluating the health status of avian species, including the endangered Bonelli’s eagle. Despite their importance, existing reference intervals (RIs) for such parameters in raptor species are frequently constrained by limited sample sizes, thus complicating clini cal interpretations. This research followed the American Society for Veterinary Clinical Pathology (ASVCP) guidelines to establish haematological and clinical biochemistry reference intervals for the Bonelli’s eagle, utilizing an indirect approach. Conservation initiatives of the Bonelli’s eagle have provided a unique opportunity to gather a high number of samples under various conditions, facilitating a comprehensive comparison between wild and captive populations. Over the course of six years, from 2016 to 2021, our research analyzed 516 blood samples collected within the frame work of a European Life Project. After rigorous data cleaning and stringent selection criteria application, a representa tive sample of 184 birds was determined. Various physiological parameters and blood lead levels were quantifed in healthy individuals. Additionally, we used Principal Component Analysis to discern distinctions between popula tions and to investigate potential interrelationships among the diverse parameters. Results We established Reference Intervals for three distinct reference groups of birds: wild nestlings (n = 72), cap tive nestlings (n = 45), and adults (n = 49). Our fndings indicate that age signifcantly afects many blood param eters. Meanwhile, gender impacts only a few parameters in adult birds. Notably, wild nestlings exhibited higher levels of AST, K, TP, and Pb in their blood compared to those bred in captivity. Conclusions This paper provides the frst reliable RI for physiological, haematological, and clinical biochemistry parameters in both nestling and adult Bonelli’s eagles. The data will augment the knowledge of the physiology of this endangered raptor, contributing signifcantly to the understanding and monitoring of both free-living birds and cap tivity programs