Livestock Drugs and Disease: The Fatal Combination behind Breeding Failure in Endangered Bearded Vultures

Blanco, Guillermo; Lemus, Jesús A.

The bearded vulture (Gypaetus barbatus) is one of the most endangered birds in Europe, with a main stronghold in the Pyrenees. Increasing declines in productivity (average number of fledglings raised per territorial pair) have recently been reported in the Spanish Pyrenees associated with habitat saturation processes [13, 14] . Given that bearded vultures may raise only one fledgling per breeding attempt, this productivity decline should be linked to increasing breeding failure when the proportion of territorial pairs that are breeding does not greatly vary with time [15] . The proximate mechanisms by which density can affect productivity have been investigated, including habitat heterogeneity, with progressively poorer territories being used, territory shrinkage and interference with breeders and floaters [13] . However, the proximate causes of breeding failure are poorly known despite the long-term interests in the conservation of this species [16] . To evaluate these causes, the examination of failed eggs and dead nestlings is imperative, including the study of the presence and impact of injury, developmental problems, poor nutritional condition, pollutants, organ damage, pathogens causing disease, etc. in order to determine the most likely cause of breeding failure.