Spatial ecology and habitat use of adult Booted Eagles (Aquila pennata) during the breeding season: implications for conservation

Abstract

Fast-moving technological advances, such as satellite tracking technologies, are providing in-depth information of aspects of avian ecology hitherto unknown. In fact, detailed information about movement ecology and ranging behaviour of birds is important not only from the perspective of the basic ecology, but also from the conservation point of view. This is particularly important in European countries where agricultural intensification, land abandonment and the withdrawal of traditional management agro-forestry practices pose a threat to biodiversity. The Booted Eagle, likewise other forest raptors, is an adequate bioindicator of human-dominated agro-forestry Mediterranean landscapes in which low-intensity traditional agricultural practices still persist. Here, using a combination of an unbiased technology (i.e., GPS telemetry), a wide geographic extension of marked birds (all over Spain), and much larger sample size than in previous works, we provide the first quantitative assessment of the home range size and space use of the Booted Eagle by means of GPS satellite telemetry during the breeding season. Interestingly, our results revealed different levels of space use over the breeding season and showed that eagles perform long distance foraging movements (i.e., [20 km) from the nest throughout the breeding season. This resulted in larger home ranges than reported thus far, and, more interestingly, in an extremely eccentric topology of territories. Hence, management measures for conservation of forest raptors based on setting restrictions around nesting sites using buffer areas of arbitrary radii clearly results in large areas of eagles' home ranges laying outside ''restriction'' areas. Therefore, conservation measures should take into account the full range of agro-forestry habitats encompassed within the home range. Finally, our results support the claim that a large-scale management approach beyond the establishment of a closed network of protected areas such as the Natura 2000 network is necessary for the conservation of Mediterranean raptors.

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

“…In Murcia the home range sizes of both sexes are greater than in Madrid, those of males being greater than for females. 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).…”

“…All booted eagles of both sexes, tagged by satellite as part of the 'Migra' project, also perform long distance movements (> 20 km) from the nest throughout the breeding season. This fact suggests that this is a common feature of this species (López-López et al 2016).…”

“…The length of the margins and the extension of the dryland crops were good indicators of the abundance of this species (Sánchez-Zapata & Calvo 1999, Díaz 2006, Martínez et al 2006. Recently, the data from the sixteen booted eagles satellite tagged as part of the 'Migra' project showed the same preferences for foraging (López-López et al 2016). In Catalonia, the results of the Catalan Breeding Bird Atlas 1999-2002(Estrada et al 2004) also showed the importance of dry cereal and other crops in the use of the habitat, which represented 31 % of the grid squares of 1 x 1 km where the species were detected, with indexes of positive selection (0.25−0.40).…”

“…For the booted eagle, home range size and habitat use has been studied in the provinces of Murcia and Madrid using conventional VHF radio-tracking (Díaz 2006, Martinez et al 2006, Díaz & Cebollada 2011. More recently, a study on spatial ecology and habitat use by sixteen booted eagles satellite tagged in the "Migra" project (López-López et al 2016), was developed in parallel and independently of this study. Undoubtedly, satellite tracking allows us to know more aspects and improve accuracy and reliability in the results on local movements and could be a good tool to help raptor managers improve the habitat management for conservation.…”

How can the home range of the Lesser Kestrel be affected by a large civil infrastructure?

“…We generated 40,000 random points within these combined MCPs and we assigned the corresponding habitat type to every random point and to every location recorded during the breeding season. To determinate habitat preferences we used Monte Carlo simulations (Manly 1997;Soutullo et al 2008;Limiñana et al 2011;López-López et al 2016), comparing the frequency of real observed locations with the expected frequencies according to random locations. These expected frequencies were calculated by sampling the same number of real locations from the generated random points; this process was repeated 1000 times using the "shuffle rows" option in Excel's PopTools add-in (Hood 2010).…”