Home range size, space use and resource selection of griffon vultures in an insular environment

Abstract

AbstractThe extent of home ranges of griffon vultures (Gyps fulvus) was studied on Crete (Greece) during 2005–2015 by monitoring 27 individuals with very high frequency radio‐telemetry. Radio‐tagged birds were followed for an average period of 13.1 months (n = 7–22), where a total of 1615 days of fieldwork produced 4420 radiolocations (x = 163.5 radiolocations per tagged bird, n = 142–328). Overall, the mean home range and mean core area of griffon vultures were estimated at 1560 ± 140 km2 (KDE 95%) and 373 ± 36 km2 (KDE 50%) respectively with significant age‐related differences within seasons. Immature griffon vultures ranged on average about double the area ranged by adults in winter and occupied significantly larger core areas. The home range overlap in per cent and utilization distribution between adult and immature birds was also significantly less in winter than in summer. Foraging griffon vultures avoided northern slopes with unfavourable flight conditions and selected sites within rangelands with low diurnal temperature variations where overwintering livestock and suitable nesting cliffs occur. Foraging adults were restricted to the vicinity of the breeding colonies and favoured sites away from urban zones. In contrast, immature griffon vultures selected pastoral zones in marginal areas with mild winters and rugged terrain. The existence of predictable food sources in combination with suitable roosting sites and favourable flight conditions were the main factors differentiating the space‐use pattern between the two age classes. We recommend that apart from the maintenance of traditional farming practices, sites, such as large communal roosts and flight corridors or entire ‘hotspot’ activity zones of immature birds, should be taken into account in conservation planning and sensitivity mapping for the species.