Studies of vigilant behavior in an urban flock of Swan Geese (Anser cygnoides) and their hybrids in Heidelberg in southwest Germany were carried out between 31 May and 22 July 2002. The habitat is characterized by a high rate of human disturbance and by artificial feeding. The following hypotheses were tested: (i) vigilance is increased due to disturbances on many occasions, (ii) vigilance should follow general patterns found in natural populations, e.g., the many-eyes hypothesis and (iii) vigilance may or may not differ between hybrids and true Swan Geese. Time spent vigilant during a 2-minute-bout of grazing averaged 15.5 s, which made up 13% of the time budget. This amount is not high compared to studies of other geese species in natural environments. There was no difference between Swan Geese and their hybrids in the duration. Vigilance was not dependent upon the number of birds present as predicted by the many-eyes hypothesis, and did not depend on the distance to water line nor position of the bird (center versus edge of the flock). Therefore, vigilance may serve other functions such as stealing food from others, detecting human passers-by with food or avoid interference between conspecifics.
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Vol. 26 • No. 3