2001 Volume 50 Issue 1 Pages 1-15,51
Spacing patterns and winter dominance relationships, including tolerance, were studied among three species of wagtails (Motacilla spp.) along the Takano and Kamo rivers in Kyoto City, central Japan from 1981 to 1983. Japanese M. grandis and Grey Wagtails M. cinerea were observed throughout the year throughout the study area, while White (Black-backed) Wagtails M. alba (subspecies M. a. lugens) were observed from October to April in the lower part of the study area, which contained residential areas. The three species occurred in pairs or as solitary birds during the non-breeding season, with the proportion of paired birds (pair ratio) highest in M. grandis, lowest (zero) in M. cinerea, and intermediate in M. a. lugens. All of the social units of M. grandis, 87.1% of M. a. lugens and 70.0% of M. cinerea remained within a particular area for at least one hour (1-hr range) during winter. The 1-hr ranges were separated for conspecific birds, but overlapped among birds of different species. The units holding 1-hr ranges were pairs and solitary birds in both M. grandis (pair ratio = 87.5%) and M. a. lugens (pair ratio = 47.6%), but only solitary birds in M. cinerea. The mean body size of the species concerned was as follows: male M. grandis> male M. a lugens > female M. grandis > female M. a lugens> M. cinerea. A relative dominance relationship prevailed as follows: male M. grandis > female M. grandis > male M. a. lugens > female M. a. lugens > M. cinerea. However, the proportions of non-response of M. grandis toward M. cinerea were higher when M. a. lugens were near M. grandis than when no M. a. lugens were nearby; M. grandis tended to ignore M. cinerea in the presence of M. a. lugens. Primarily the body size, and secondarily the dependent status seem to determine the intersexual and interspecific dominance hierarchy. The difference in microhabitat, and interspecific relationships in dominance and tolerance may enable the three wagtail species to coexist in one area. Territory defendability resulting from such intersexual and interspecific dominance relationships is thought to determine whether a wagtail species occurs in a pair or not during winter.