The adaptive significance of crèching behaviour in the white-winged scoter (Melanitta fusca deglandi)

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Abstract
I tested several hypotheses regarding the adaptive significance of crèching behaviour using white-winged scoters (Melanitta fusca delgnadi) at Redberry Lake, Saskatchewan. Scoter crèches consist of a single female tending the young of one or more conspecifics. There was no relationship between a female's weight at the end of incubation and whether she stayed with ducklings. Therefore, there is no evidence that females in poor condition abandon their young more frequently than other females. No relationship was found between a female's age and her association with ducklings. Therefore, crèching does not appear to be related to female age or experience. Observations of color-marked ducklings in 1985 showed that 7 out of 10 females tended crèches that were composed entirely of fostered young. The survival of ducklings from large groups was greater than that from small groups, so crèching does not appear to be a strategy that enhances individual fitness of crèche-tending females. However, because of the high degree of philopatry displayed by female scoters, crèching could enhance inclusive fitness if crèches contain the young of related individuals. This hypothesis could not be tested.