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Capsule Arrival fuel load of migratory passerine birds after the Sahara crossing in spring varied between oases of different habitat quality.

Aims To test: (1) if spring migrants reaching northern Africa with low fuel stopover in oases of species-specific suitable habitat; (2) whether migrants have sufficient fuel loads to reach southern Europe; and (3) if there is local variation.

Methods We collected data from passerines caught at three different oases in southeast Morocco during the spring of 2011.

Results In species typical of mesophilic vegetation in Europe, birds carrying lower fuel loads occurred at a stopover site with lusher vegetation than two oases located further south. By contrast, in species adapted to xerophilic vegetation, birds carrying high fuel loads were found in drier habitat.

Conclusion When arriving in northern Africa, migrants stopover in oases of different habitat quality in a species-specific fashion. Fuel load is, except for a few Mediterranean species, sufficiently high to reach the south of Europe without needing to refuel. Significant differences between oases suggests that fuel loads of birds from a single site are non-representative of the entire region.