Behaviors Associated with Seasonal Reproduction and Long-Term Monogamy in Canada Geese

Abstract

We measured seasonal changes in the incidence of various social behaviors performed by members of a captive flock of Canada Geese (Branta canadensis moffitti) in order to determine (a) which of these behaviors were associated with reproduction in a species with long-term monogamy, (b) sexual differences in their expression, and (c) their temporal relationship with nesting events. Breeding and nonbreeding geese were compared. Aggression, Triumph Ceremony, and Calling by breeding male geese reinforced pair bonds and were performed most frequently in the context of territorial display. The Triumph Ceremonies of breeding females also strengthened pair bonds and were probably essential for establishing a territory and reproductive success. Breeding males behaved aggressively most frequently before the initiation of nesting through the incubation period. During incubation, females became increasingly unresponsive to their mate's Triumph Ceremony and by the time their goslings were two weeks old the frequency of their aggressive behaviors was closer to that of their mates than at any other time of the year. These changes coincided with an increase in social gregariousness during brood rearing and molt. Retreat was more common in nonbreeding than breeding geese. Nonbreeding males were not aggressive and performed few Triumph Ceremonies. Their behavior did not elicit supportive responses from nonbreeding females and probably inhibited pair formation. The timing of reproduction of many avian species in seasonal habitats is confined by the periodic availability of resources (Lack 1968). Canada Geese (Branta canadensis) nest predominantly in northern latitudes (Delacour 1954, Palmer 1976) and reproductive events occur within a relatively short period of time. Nesting generally begins as soon as secure nest sites become available, and growth of goslings coincides with the growth of sedges and grasses during the summer (Maclnnes 1962, Vermeer 1970, Maclnnes et al. 1974, Raveling and Lumsden 1977, Raveling 1978). The timing of nesting is also influenced by intra-pair activities (Lofts and Murton 1973:81, Silver 1978) and social conditions (Lott et al. 1967). Formation of life-long pair bonds and intensification of mutual behaviors by pairs of Canada Geese before arrival on their breeding grounds permit nesting to begin without the delay of pair formation. The social behavior of Canada Geese is well documented (e.g., Hanson 1953, Collias and Jahn 1959, Klopman 1962, 1968, Brakhage 1965, Raveling 1970), but few investigators have quantified such behavior using individuals with known histories in a well defined social environment. In this paper, we report the frequency with which previously described behaviors were performed by breeding and nonbre ding Canada Geese (B. c. moffitti). Our objective was to identify behaviors that were important to intra-pair synchrony and nesting success in order to increase our understanding of the behavioral role of the sexes in a species that has long-term pair bonds and nests within a restricted period of time.