Among Accipitriformes sensu stricto, only a few species have been reported to form hybrid zones; these include the red kite Milvus milvus and black kite Milvus migrans migrans. M. milvus is endemic to the western Palearctic and has an estimated total population of 20–24,000 breeding pairs. The species was in decline until the 1970s due to persecution and has declined again since the 1990s due to ingestion of rodenticide-treated baits, illegal poisoning and changes in agricultural practices, particularly in its core range. Whereas F1 M. milvus × M. migr. migrans hybrid offspring have been found, F2 and F3 hybrids have only rarely been reported, with low nesting success rates of F1 hybrids and partial hybrid sterility likely playing a role. Here, we analyzed the mitochondrial (CO1 and CytB) and nuclear (Myc) DNA loci of 184 M. milvus, 124 M. migr. migrans and 3 F1 hybrid individuals collected across central Europe. In agreement with previous studies, we found low heterozygosity in M. milvus regardless of locus. We found that populations of both examined species were characterized by a high gene flow within populations, with all of the major haplotypes distributed across the entire examined area. Few haplotypes displayed statistically significant aggregation in one region over another. We did not find mitochondrial DNA of one species in individuals with the plumage of the other species, except in F1 hybrids, which agrees with Haldane´s Rule. It remains to be investigated by genomic methods whether occasional gene flow occurs through the paternal line, as the examined Myc gene displayed only marginal divergence between M. milvus and M. migr. migrans. The central European population of M. milvus is clearly subject to free intraspecific gene flow, which has direct implications when considering the origin of individuals in M. milvus re-introduction programs.

Black kites of the nominal subspecies Milvus migrans migrans breed in the Western Palearctic and in Central Asia, while the European population is relatively small. The birds winter mostly in sub-Saharan Africa. Until 2000 winter observations of black kites were rare in Greece, and also within the tri-point border area of Austria, the Czech Republic and Slovakia. At that time regular wintering of black kites started there. These data and evidence from recent local literature as well as from a number of unpublished data obtained throughout European countries and reviewed in this paper corroborate the impression that numbers of black kites wintering in Europe and the whole Mediterranean area including Turkey are increasing. The reasons considered are climate warming in the area and some negative changes in sub-Saharan Africa in the traditional wintering grounds of black kites. Notes about the wintering of black/red kite hybrids are also added.

No abstract

The winter months are an important part of the year for raptors as survival throughout this period is critical for the succeeding year's population recruitment. We reveal novel insights into the wintering of kites (Milvus spp.) on the Mediterranean island of Crete, Greece. We use a combination of 1) direct field observations, 2) online photograph searches and 3) analysis of satellite telemetry data from a tagged hybrid Red Kite × Black Kite (Milvus milvus × M. migrans migrans). The number of observations of wintering kites has increased since 1998. The wintering of numerous Black Kites with morphological features of both subspecies (M. migrans migrans and M. migrans lineatus) and a hybrid Red Kite × Black Kite is a new phenomenon on Crete.

No abstract