Breeding in Three Species of Fairy-Wrens (Malurus): Do Helpers Really Help?

Abstract

About 240 h were spent observing behaviour at the nests of co-existing Superb Malurus cyaneus, Variegated M. lamberti and White-winged M. leucopterus Fairy-wrens. Feeding rates increased as nestling number increased but not proportionately. Variegated Fairy-wrens shared feeding about equally between the sexes but in the other two species the females were the predominant feeders except when nestlings were very young. There was a correlation between feeding rate and age of nestlings. Superb Fairy-wren helpers were young of the year and contributed most when nestlings were older whereas with White-winged helpers (all adult males) the pattern was reversed. Adults and helpers 'complemented' each other so that the total number of feeds per hour to the nestlings was more stable than any one individual's contribution. Helpers did not lead to an increased feeding rate but rather a decrease in the female's feeding rate and load carried.