Geographic range estimates and environmental requirements for the harpy eagle derived from spatial models of current and past distribution

Long-term female bias in sex ratios across life stages of Harpy Eagle, a large raptor exhibiting reverse sexual size dimorphism

The primary (PSR), secondary (SSR) and adult (ASR) sex ratios of sexually reproducing organisms influence their life histories. Species exhibiting reversed sexual size dimorphism (RSD) may imply a higher cost of female production or lower female survival, thus generating biases in PSR, SSR and/or ASR towards males. The Harpy Eagle is the world's largest eagle exhibiting RSD. This species is found in the Neotropical region and is currently threatened with extinction. We used molecular markers to determine the sex of 309 Harpy Eagles spanning different life stages-eaglets, subadults and adults-from 1904 to 2021 within the Amazon Rainforest and Atlantic Forest. Sex ratios for all life stages revealed a female-biased deviation across all periods and regions. Our results suggest that the population bias towards females is an evolutionary ecological pattern of this species, and SSR and ASR likely emerged from the PSR. This natural bias towards females may be compensated by an earlier sexual maturation age of males, implying a longer reproductive lifespan and a higher proportion of sexually active males. A better understanding of the Harpy Eagle's life history can contribute to understanding sex-role evolution and enable more appropriate conservation strategies for the species.

Predicting the potential distribution of a near-extinct avian predator on the Arabian Peninsula: implications for its conservation management

Species distribution models (SDMs) generate predicted distribution maps which can be used as effective tools for conservation purposes. The persistence of isolated populations at the margin of a large distributional area depends on local threats which may differ from those faced by the main population. Environmental predictors can indicate suitable areas for these species and, indirectly, evaluate the impact on peripheral populations due to fragmentation and isolation. The Lanner Falcon (Falco biarmicus) is an Afro-tropical and Mediterranean polytypic species considered critically endangered (CR) in Arabian Peninsula by IUCN, but a lack of published information about its distribution persists. Here, we model the distribution of the Lanner Falcon in the Arabian Peninsula using nest-site data and map its core area and their habitat suitability using a robust algorithm with good prediction accuracy even at low sample sizes (MaxEnt). The predictive map suggests a potential distribution of the Lanner Falcons that runs from north to south along the eastern coast of the Red Sea. The Terrain Roughness Index contributed the most to the breeding range model predictions (57.6%), followed by isothermality (Bio3, 15.3%). The model suggests a tendency by Lanner Falcons to occupy areas with a low terrain complexity according to their behavioural patterns and breeding strategies. In addition, this falcon is highly sensitive to climate occupying high isothermal regions in order to avoid extreme heating events. Overall, predictive models indicate a narrow range of suitable environmental conditions for breeding as well restricted favourable areas during dispersal and migration. Thus, these small and fragmented populations are more likely prone to anthropogenic factors and must be buffered against them.

Birds adapted to cold conditions show greater changes in range size related to past climatic oscillations than temperate birds

Investigation of ecological responses of species to past climate oscillations provides crucial information to understand the effects of global warming. In this work, we investigated how past climate changes affected the distribution of six bird species with different climatic requirements and migratory behaviours in the Western Palearctic and in Africa. Species Distribution Models and Marine Isotopic Stage (MIS) 2 fossil occurrences of selected species were employed to evaluate the relation between changes in range size and species climatic tolerances. The Last Glacial Maximum (LGM) range predictions, generally well supported by the MIS 2 fossil occurrences, suggest that cold-dwelling species considerably expanded their distribution in the LGM, experiencing more pronounced net changes in range size compared to temperate species. Overall, the thermal niche proves to be a key ecological trait for explaining the impact of climate change in species distributions. Thermal niche is linked to range size variations due to climatic oscillations, with cold-adapted species currently suffering a more striking range reduction compared to temperate species. This work also supports the persistence of Afro-Palearctic migrations during the LGM due to the presence of climatically suitable wintering areas in Africa even during glacial maxima.

Rhabdoid melanoma in a harpy eagle (Harpia harpyja)

A 28-year-old male harpy eagle (Harpia harpyja) with a history of anorexia, hyporexia, lethargy, and progressive weight loss was found dead and submitted for post-mortem examination. Gross findings include dark brown discolouration of testes and lungs; the testes were bilaterally enlarged, glistening brown-grey to blackish in appearance, firm, smooth, and multilobulated. The lungs contained a mass with similar features to the testicles, irregularly shaped with multiple nodules. Histology of testis showed round, polygonal and pleomorphic cells, containing melanin pigments and a typical eosinophilic vacuole in their cytoplasm and with severe pleomorphism. An immunohistochemistry panel with Melan-A, vimentin, CK AE1/AE/3, MUM-1 and CD-68 were performed, yielding a positive reaction for Melan-A and vimentin. The morphology of the tumour cells, the presence of melanin pigment and the immunoreactivity for Melan-A and vimentin by the cells led to a diagnosis of rhabdoid melanoma. This is the first case of this pathology in the testis with lung metastasis in a harpy eagle.