Relatieve vleugellengte bij Puffinus p. puffinus, Puffinus p. mauretanicus en Puffinus griseus

Many experienced Dutch seawatchers feel themselves capable of identifying every shearwater they see regardless of the distance at which it passes by. One of the most frequent criteria used to support these identifications is the contention that the Sooty Shearwater would have relatively longer wings than the Manx in relation to body length. The data in table 1 ( cited from Cramp & Simmons 1977 and Harrison 1983) however clearly indicate that this is not at all true. We therefore suggest that observers should be aware of this fact and consequently be more conscious and careful in identifying the often very far-off shearwaters. Presumably really experienced observers do not make many mistakes, but the criteria they use seem to be more subjective than they might know.