GPS tracking of Red Kites (Milvus milvus) reveals fledgling number is negatively correlated with home range size

Abstract

To date, reliable studies on the spatial area use and home range size of the Red Kite (Milvus milvus) during the breeding season are lacking. Between 2007 and 2014, 43 adult individuals were fitted with GPS transmitters in Germany. The home range sizes of 27 males, which successfully reared 47 broods, ranged between 4.8 and 507.1 km 2 based on the 95 % kernel utilization distribution. The median during the nestling and post-fledging dependent periods was 63.6 km 2 . The home ranges of 12 females, with a total of 21 successful broods, ranged between 1.1 and 307.3 km 2 . Within a single breeding season, there were considerable differences among home range sizes. There was also considerable variation in the home range size of adults during the course of a season. Across years, the median home range size of all males ranged between 21 and 186 km 2 , depending on prey availability. For individual males at the same nest site, the home range size varied up to a factor of 28 across years. Kites with very large home ranges had only one fledgling, which indicates that resources were scarce. Individuals with more nestlings had intermediate-sized to small home ranges. The relationship between the number of fledged young and home range size was modelled using a cumulative logit model. Fifty-six, 37, and 26 % of male kite fixes were beyond a 1, 1.5, and 2 km radius around the nest, respectively. Birds with very small or very large home ranges differed considerably from these average figures. Adults sometimes travel very long distances to visit distant grasslands during and shortly after mowing (up to more than 34 km) from the nest, due to the increased likelihood of prey availability at these sites. In conclusion, home rage size serves as a useful indicator of Red Kite habitat quality, which may provide key conservation information at the wider ecosystem level.

Study on the foraging behaviour of the European nightjar Caprimulgus europaeus reveals the need for a change in conservation strategy in Belgium

“…In our study habitat composition influenced nightjars’ home range size, and results of previous studies suggest that food availability determines nightjars’ foraging distance (Sierro et al , Sharps et al ). In cases of landscape heterogeneity (Camacho et al , Godet et al ) or where the distribution and availability of food resources fluctuates (Penteriani et al , Pfeiffer and Meyburg ), home range size can be affected. However, it is unclear how these factors influence nightjars’ foraging behaviour on a northwestern European scale.…”

Density‐dependent effects on reproductive performance in a recovering population of White‐tailed Eagles Haliaeetus albicilla

“…The concomitant reduction in the availability of favourable foraging habitat in the close vicinity of nesting sites thereby increases foraging distances and possibly reduces adult fitness and the time available for defence of nests. This in turn should result in a lower proportion of successful broods and a lower survival of nestlings (also see Pfeiffer & Meyburg 2015 for Milvus milvus). These findings are in line with the habitat heterogeneity hypothesis and support the findings of previous studies suggesting that as a consequence of increasing population density birds have been increasingly forced to breed in suboptimal habitats (Ferrer & Donazar 1996, Both 1998, Fernandez et al 1998, Kr€ uger & Lindstr€ om 2001, Carrete et al 2006, Kr€ uger et al 2012).…”

Factors influencing the movements during the breeding season of a female booted eagle (Aquila pennata) tagged by satellite in central Catalonia (Spain)

“…More recently, López-López et al (2016) found that the median value of home ranges of sixteen booted eagles, tagged by satellite as part of the 'Migra' project, was more extensive than those mentioned before for Murcia and Madrid, and showed no significant differences between sexes. In the same way, for red kites (Milvus milvus) the home ranges obtained by direct observation and VHF radio tracking tend to be smaller than those obtained using GPS satellite technology, because these methods do not allow data to be obtained from flights further away from the nest (Pfeiffer & Meyburg 2015). Home range sizes depend on many factors such as the availability of food, the quality and suitability of the habitat, intra-and inter-specific competition or how far away the food sources are from the nest (Newton 1979).…”

“…Satellite tracking has been shown to be an effective and accurate tool for studying so far untreatable or insufficiently known aspects of the biology of birds, such as fidelity to territories, mortality, habitat use and the extent of their territories (see Meyburg et al 2006, Margalida et al 2008, Hernández-Pliego et al 2014, Pfeiffer & Meyburg 2015, among many others). In order to study its migration, satellite telemetry was first used with the booted eagle Aquila pennata in 2006, when two adult females were marked in the community of Madrid for which data during the breeding season of a female booted eagle (Aquila pennata) tagged by satellite in central Catalonia (Spain) were received from their autumn migration and wintering in Mauritania and Mali respectively (Diaz & Cebollada 2011).…”