Abstract
To develop effective conservation strategies for migratory birds, it is essential to understand the ecology of a species at each biological phase, including its wintering (or non-breeding) season. For the red kite (Milvus milvus), an endangered raptor from the Western Palearctic, its wintering ecology is little known. We tagged 44 red kites using GPS/satellite transmitters to study their non-breeding seasons in Spain. Two spatial strategies were recorded: 34 individuals (77%) spent all their wintering periods in only one area, whilst the remaining individuals (23%) moved between two main areas at least once. This strategy, however, was not consistent over the years. In the latter case, the distance between wintering areas was 311.6 ± 134.7 km, and individuals usually spent equally long periods in each area (96 ± 35 days). No effects of age or sex were found on these area shifts, so they may have been driven by food or habitat resource availability. We also found high interindividual variability in home range sizes. The home ranges of adults were two- to three-times smaller than those of immatures, probably due to a better knowledge of the territory.
Highlights
SEO/BirdLife, Bird Monitoring Unit, C/Melquiades Biencinto 34, E-28053 Madrid, Spain; Technisches Büro für Biologie Mag
Our work demonstrated a dual strategy of the red kites’ wintering in Spain: most individuals remained in only one area, but some of them changed their wintering area within one wintering season, without increasing the duration of the wintering season
We found a high variability in the home range sizes of the wintering red kites
Summary
SEO/BirdLife, Bird Monitoring Unit, C/Melquiades Biencinto 34, E-28053 Madrid, Spain; Technisches Büro für Biologie Mag. Satellite/GPS telemetry has increased the understanding of how individuals interact with their environment [4] This technology has been used to study the wintering areas on many migratory raptors, such as the pallid harrier [5], the Eleonora’s falcon [6,7], the Egyptian vulture [8] and the booted eagle [9]. They frequent garbage dumps, slaughterhouses or areas where they can find carrion and other organic remains [19,20] These scavenging habits, together with their semi-colonial behaviour, are a serious problem for the conservation of the species as a consequence of the poisons that can be found in these food sources [21]. Europe holds at least 90% of the global red kite population, with 24,000–31,900 pairs breeding in 17 countries and a winter population size of 38,100–42,200 individuals [22]
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