A new paper (Margalida et al. in 2016, Scientific Reports) showed that the use of space differs in bearded vultures, particularly between territorial and non-territorial birds, but there was no seasonal effect. The authors analyzed the movements of 19 bearded vultures in the Pyrenees tracked with GPS between 2006 and 2014, from which more than 66,000 GPS locations could be obtained.
Their analysis revealed that territorial bearded vultures exploited home ranges of about 50 km2, while non-territorial birds used areas of around 10,000 km2. Furthermore, the mean daily movements (23.8km vs 46.1km) and the maximum travelled distance per day (8.2 km vs 26.5km) was also different between these two groups of birds. Interestingly, territorial females moved greater distances (12 km) than males (6.6 km), while the maximum distance travelled by a bearded vulture in one day was a staggering 260 km. Pyrenean bearded vultures have smaller home ranges than their south-African cousins.
The study confirmed the authors´ prediction that movements in the non-breeding and breeding periods are similar because the poor weather in winter is compensated for by a network of supplementary feeding sites that function principally during the breeding season. On the other hand, the summer (non-breeding) period offers greater food availability during the transhumance season.
In relation to the presence of supplementary feeding sites (SFS) and spatial use, the authors found only 5% of the tag locations were within 1km of the SFS, suggesting birds have plenty of food available in the wider mountains. Further, they found that non-territorial bearded vultures included more SFS in their home ranges than territorial individuals, which did not have any SFS in their core, high-use territory. Furthermore, inexperienced individuals included more SFS in their movements because they act as predictable food supplies. The authors suggest that territorial birds use less SFS because they exploit unpredictable but higher-quality prey more efficiently.
Another interesting find is that between 46% (territorial bearded vultures) and 54% (non-territorial birds) of home ranges were outside protected areas.
The largest natural European population of bearded vultures is in the Pyrenees and knowledge of the movement of this species will help improve management actions aimed at increasing the distribution of this species and minimizing the risk of metapopulation extinction. The identification of the core areas this vulture uses is an important step in the conservation of the species and will improve management strategies.
You can download the publication below.
Photo: Bruno Berthémy/VCF