Wednesday, November 23, 2011

Satellite tracking Eleonora’s falcons, Montagu’s harriers and Egyptian vultures

Satellite tracking and remote sensing technologies unravel conservation problems of European raptors wintering in Africa

November 2011. Populations of migratory species can be affected by events occurring in distant and different parts of the world, and a bulk of studies suggest that long-distance migratory birds are declining at a faster rate than other species. Unfortunately, our knowledge of the ecology of migratory birds has been constrained by the difficulties in tracking individuals across seasons.

Satellite tracking advances
Nevertheless, advances in the miniaturization of satellite tracking devices are now making it possible to determine the connections between the different seasonal grounds of birds in a way unimaginable few years ago. Moreover, the availability of fine-scale digitalized land use and climate maps obtained through remote sensing allow biologists to analyze the habitat preferences of those birds and model their distribution.

Eleonora's falcon, Montagu's harrier and Egyptian vulture
The research group of the Estacion Biologica Terra Natura (University of Alicante, Spain) recently published the first papers dealing with habitat use of European satellite-tracked raptors wintering in Africa: the species involved are the Eleonora's falcon, that spent the winter in Madagascar, and the Montagu's harrier and the Egyptian vulture in the Sahel (West Africa).

Eleonora's Falcon
Eleonora's Falcons wintering in Madagascar selected degraded humid forests and cultivated areas close to pristine humid forest. They showed a preference for these land use types within areas where pristine humid forests were the most abundant habitat type. These falcons could be taking advantage from a spill-over edge effect of their insect prey into open areas close to humid forests. Therefore, the importance of humid forests for Eleonora's Falcons seems to be high. The current loss of this habitat in Madagascar is a cause for concern with respect to the conservation of this long-distance migratory falcon species.

Montagu's harrier
Montagu's harriers occupied a large region encompassing a total of eight countries. The most preferred habitats were croplands and grasslands. Protected areas only covered a small proportion of the overall wintering grounds of tracked harriers and the most suitable areas for the species in Western-Central Sahel. Increasing the extent of preferred natural habitats within protected areas should benefit the conservation of this and probably other insect-eating raptors. Conservation actions in the region should therefore be mostly focused on improving land use planning and management outside protected areas, specially enhancing agricultural practices to make biodiversity conservation compatible with poverty alleviation.

Egyptian vultures
Similar results were also recorded for the Egyptian vultures. The species winters in the transitional Sahelian eco-region which is composed of a mosaic of semi-arid grasslands, savannas, steppes, and thorn scrublands where traditional semi-nomad shepherds raise livestock in a system of transhumance, which is taken advantage of by Egyptian Vultures. Similarly to Montagu's harriers, these areas are located in southern Mauritania, along the Senegal border and in Central Sahel region.

Site fidelity
In all the three species, the individuals showed a high degree of site fidelity, occupying roughly the same areas in consecutive years. These data, coupled with other ongoing studies, will facilitate the conservation of these European long-distance migratory species also outside of their breeding range.

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