M. V. Lomonosov Moscow State University
Faculty of Biology, Department of Vertebrates Zoology
119234 Moscow, Leninskie Gori, MSU, 1
The spatial organization of the bill tip organ in waterfowl was studied. 327 specimens of 35 species from tribes Anserini, Aythini, Mergini, Tadornini, and Anatini (order Anseriformes) were investigated. Two types of tactile epithelial formations, sensillar and asensillar, were revealed on the tips of the upper and lower jaws. The number of the mandibular formations always prevails over the maxillary one. The combinations of the upper and lower tactile formations number differ significantly among the majority of investigated tribes. The anseriform species can be divided into three different types based on combinations of these indices according to different foraging techniques. They are: grazing (geese, swans, sheldgeese), pursuit diving (sea ducks), and dabbling (pochards, shelducks, dabbling ducks). The formations density per square mm correlates with the asymmetry of the bill tip organ (r =0.55; p < 0.01; n = 327). The correlation is the greatest in dabbling species. The probable bill tip organ's function, besides location and analysis of food particles, lies in the fact that dabbling species can communicate with each other by means of their motions in the course of food intake. It helps them to save time and to optimize their individual distances when feeding in darkness.