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♦ ¹Assessing the diet of nestling Bearded Vultures: a comparison between direct observation methods, Antoni Margalida, Joan Bertran, and Jennifer Boudet, J. Field Ornithol. 76(1):40–45, 2005
♦ ²Changes in the diet of Great Black-backed Gulls Larus marinus on Skomer Island 1958- 1992, Jim Poole, SEABIRD 17; 50-55