Chromosomal inversions can contribute to genetic differentiation and ecological adaptation. In common quails (Coturnix coturnix), a large chromosomal inversion encompassing over 1,200 genes is associated with key phenotypic traits, including increased body size, darker throat pigmentation, and reduced flight efficiency, which may influence migratory behavior. We hypothesized that this inversion could be associated with the presence of resident birds in the southwest of the species’ European distribution, where the inversion has been found in high frequency. We surveyed one wintering population in southern Spain and analyzed the genomic composition, morphology, and deuterium, nitrogen and carbon stable isotope composition of primary feathers. Our results revealed the coexistence of birds with different karyotypes and morphologies that also differ in migratory behavior, as inferred from the comparison of the stable isotope signature in feathers. While quails with the inversion showed limited evidence of migratory movements, quails without the inversion seemed to have reached the area from higher latitudes. Interestingly, our results also revealed that these migratory quails that reached this population in winter had differences in their diet. Thus two separately evolving chromosomal lineages, characterized by the presence/absence of the inversion, coexist in the wintering area leading to differences in morphology, behavior and resource use. Due to the lack of recombination in the inversion, the divergence is expected to continue increasing.

Haemosporidians are among the most common parasites in birds and often impact negatively host fitness and consequently can affect entire host populations. It is therefore important to determine what factors influence parasite prevalence, particularly if they are caused by anthropogenic activities. Here we explore the effect of temperature, forest cover, and proximity to anthropogenic disturbance on haemosporidian prevalence and host-parasite networks on a horizontal spatial scale, comparing four fragmented forest patches and five localities within a continuous forest in Papua New Guinea. We find that the majority of Haemosporidian infections are caused by the genus Haemoproteus and that avian-haemosporidian networks are more specialized in continuous forests. At the community level, only forest cover was negatively associated with Haemoproteus infections, while abiotic and anthropogenic effects on parasite prevalence differed between bird species. We further tested if prevalence and host-parasite networks differed between the canopy and the understorey (vertical stratification) and found significantly higher Haemoproteus prevalence levels in the canopy, and the opposite trend for Plasmodium prevalence. This implies that birds experience distinct parasite pressures depending on the stratum they inhabit, likely driven by differences in vector communities. These three-dimensional analyses of avian-haemosporidians at horizontal and vertical scales provides a deeper understanding of the environmental factors driving haemosporidian prevalence in tropical lowland forests of New Guinea. Collectively, our results suggest that the effect of abiotic variables on haemosporidian infections are species specific, and that factors influencing community-level infections are primarily driven by host community composition.