Zeekoet Uria aalge met afwijkende veerstructuur

On 5 February 1990 a freshly dead and slightly oiled Guillemot was found on the beach near Egmond aan Zee. In the right wing all primaries consisted of almost bare shafts, which were split longitudinally. Also, of the tips of the upper primary coverts only a bare shaft was present. The outermost primary had just started growing. Other feathers were of a normal structure. On 3 March 1984 a similarly deformed dead Guillemot was found on the Dutch coast. In this bird, both wings had aberrant primaries as well as some deformed secondaries. Although several explanations have been suggested for these deformations, Bourne (1974) showed that the deformations are caused by cleaning activities from birds which are lightly polluted by oil. Indeed no oil was found on the wings but the birds died anyway because they were probably severely hampered in foraging and flying.