Parental Behavior of Cackling Canada Geese during Brood Rearing: Division of Labor within Pairs

Behavior of pairs of Cackling Canada Geese (Branta canadensis minima) was studied on the Yukon-Kuskokwim Delta, Alaska, during the brood-rearing period in 1978 and 1979. Foraging time consisted of cycles of alert postures followed by periods of grazing, when individuals searched for, or consumed, food. Females had shorter alert periods (x̄ = 5.58 sec) than males (x̄ = 8.04 sec) during all four possible time periods (two time periods in each of 2 years), although differences were significant in only one of these periods. Females also had significantly longer grazing periods than males (x̄ = 10.67 sec vs. 8.42 sec) during three of the four time periods. Females spent an average of 74% and 58% of foraging periods actually grazing prior to and during the molt, respectively, whereas males spent only 52% and 58% of foraging time grazing during these two time periods. Less vigilance by females relative to males resulted in females spending a greater percentage of their total time budget grazing, although the difference was significant only before the molt in 1979. The proportion of foraging periods in which adults were alert was positively related to the number of goslings in their broods for both sexes, but when pairs associated with no goslings were removed from the analyses, the relationship was no longer significant for females. These data support the hypothesis that long-term monogamy in geese is beneficial in part because males are able to assume greater responsibility for vigilance after hatching, allowing females to replace depleted protein and lipid reserves. The relationship between alert behavior and brood size does not support a recent model of parental investment which predicts no such relationship (Lazarus and Inglis 1986).