Blood parasites in Eleonora’s Falcon revisited: new insights from the eastern Mediterranean support transmission outside the breeding niche

Abstract Host–parasite interactions can shape avian population dynamics, and blood parasites can serve as useful markers of host movements across transmission landscapes. Eleonora’s Falcons ( Falco eleonorae ) occupy multiple biomes annually and, owing to their long-distance migration and unusual late-season breeding, may encounter diverse haemosporidian parasites. Until now, the haemosporidian assemblage of eastern populations had not been analyzed by DNA studies. We examined 321 individuals from two islands in southern Greece hosting a substantial number of breeding pairs in the country (Antikythera: 2017–2024, Paximada: 1991–2001) using nested-PCR amplification and Sanger sequencing to identify haemosporidian infections. Overall haemosporidian prevalence was 15%, with 11 distinct lineages detected. Infection probability did not differ by sex, color morph, or season or sampling period. Nestlings were not infected, supporting the absence of local transmission in the species’ exposed marine cliff-breeding habitat. Several lineages (e.g., pLK05, pLK06, hBUBIBI01, hBUTBUT04, and lCIAE02) matched those previously reported from western populations, suggesting shared transmission areas along shared stopover sites and/or wintering grounds in Africa. Other lineages—such as Haemoproteus tinnunculi hFALSUB01 and the Leucocytozoon lineage lBNOW04—are newly documented in Eleonora’s Falcons and appear more common in eastern populations, indicating acquisition in regions used predominantly during the pre-breeding period. Rare singletons (pRTSR1, pACCTAC01, pSYBOR10, and hPADOM03) may represent spill-over or low-intensity infections acquired at Mediterranean or African sites. Our findings show higher lineage diversity than documented in Spain and highlight how information on haemosporidian assemblages and population-specific transmission areas can complement each other and refine our understanding of host–parasite connectivity across continents.