The effects of supplemental feeding on Eurasian Griffon range from increased survival and reproduction to population recoveries. In 2000, the appearance of Bovine Spongiform Encephalopathy (BSE) in Europe resulted in the implementation of the 1774/2002 regulation that required carcass removal and incineration at processing plants within the European Union and resulted in an immediate reduction of food availability for scavengers. We wished to evaluate the effect of the implementation of the reduced food availability on the scavenging Eurasian Griffon population. The study was conducted in La Rioja province (northern Spain). Eurasian Griffon fledglings are regularly brought to a rehabilitation center and can help evaluate the changes in nutritional condition before and after the enactment of the BSE regulations. A total of 47 first year griffons were sampled. Ptilochronology was applied to the rectrices, growth bars that are grown during the fledgling period were counted among nestlings before and after implementation of the EU-BSE directives. We found that the width of the growth bars, that represent the nutritional condition of the bird, showed significant differences over time. The growth bars before the implementation of the BSE EU-directives were significantly narrower than the subsequent period wherein carcasses were greatly reduced. The frequency of fault bars showed trends opposite to those of growth bars and there were significantly more fault bars in the pre-removal implementation period than the post-removal period. In conclusion, we consider this to be a result wherein the local adults with fidelity to their breeding colonies remained in the area while the non-breeding sub-adults and floaters have strayed in search of food. This has resulted in reduced inter-and intra-specific competition and only adults in good body condition breed resulting in healthier fledglings.
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Vol. 47 • No. 2