2026/06/25 by Matías A. Juhant, Miguel D. Saggese · 1 voice
Environmental Science · Immunology and Microbiology · #Abundance (ecology) #Age groups #Age structure #Avian ecology and behavior #Bird parasitology and diseases #Lesion #Overwintering #Wildlife Ecology and Conservation
paper · doi:10.1080/15594491.2026.2688599
openalex publication_date 2026/06/25 · openalex created_date 2026/06/26 · openalex updated_date 2026/08/04
Understanding patterns of abundance and anthropogenic-induced stressors in free-ranging raptors remains challenging due to the difficulty of assessing both abundance and the occurrence of physical lesions in the same populations. However, field photography offers a practical, non-invasive approach to evaluate these traits at specific sites. We conducted 209 h of observation and photographic surveys over four austral winters at two anthropogenic food-rich sites separated by 1,750 km in Argentine Patagonia. We assessed the number of individuals, age structure, and age-specific lesion types and prevalence in overwintering Black-chested Buzzard-Eagles (Geranoaetus melanoleucus). We found that: (1) a minimum of 394 individuals overwintered at these sites; (2) the age structure of counted individuals differed markedly between sites and across time periods, with the northern site (surveyed in 2022 and 2023) slightly skewed toward younger age classes, whereas the southern site (surveyed in 2014 and 2016) was strongly dominated by the oldest age class; (3) 22% (86 of 394 individuals) exhibited lesions, primarily affecting the hindlimbs (e.g. missing legs, digits or talons, and swollen tarsometatarsus-digits joint or digits); (4) among the 86 affected individuals, a total of 102 lesions were documented, yielding a ratio of 1.19 lesions per individual; (5) lesion prevalence was more than twice as high at the southern site (60 of 191 individuals; 31%) compared to the northern site (26 of 203 individuals, 13%); and (6) swollen tarsometatarsus-digits joint or digits was the most prevalent lesion type at both sites, showing no differences among age classes at the northern site, whereas at the southern site it was significantly higher in the oldest age class. Together, these results indicate potential site- or year-specific differences in age structure and age-specific lesion prevalence in overwintering Black-chested Buzzard-Eagles in Patagonia.