The influence of nests on the social behaviour of males in Manorina melanocephala, a communally breeding honeyeater

Abstract

Manorina melanocephala is a communally breeding honeyeater in which several males feed the offspring of a single female. A free-living population of colour-banded birds was observed from 1971 to 1974 m southern Queensland.

Males visiting nests were frequently attacked by males previously dominant at that place. Immatures from a female's previous broods in the same year were driven away from the nest by adult males. Some- times males displayed towards the eggs in the nest and often drove off the incubating female before such display.

Females almost never visited the nests of other females and only rarely fed their fledged offspring. Females appeared to learn to leave the nests at the approach of a male and thus incubation could possibly be considerably interrupted when many males visit. Every nest watched had a complement d visiting males, whose number increased as the nest advanced. At least twenty-two males were known to visit one successful nest. Feeding rates of nestlings by males reaching fifty-five per hour; of fledgelings eighty per hour. Females' contributions were additional to these. Males did not restrict their activities to a single nest but often had a much more active role at one. The largest recorded complement (banded males only) attending successive nests of a single female in the same breeding period numbered twenty-four.

Spaces in which females were active showed no clustering nor were they confined to the area occupied by a coterie of males. Of nests built by fourteen banded females, an average of 5.2 were visited by thirty-three banded males during systematic watches. The mean number of females visited was 3.8. Males ranking highest in visiting any female also visited more nests and more females than did lower ranking males. No male ranked highest with more than one female. Often females were visited by males from more. than one coterie but then always from an adjacent one. When a female nested within the area of a coterle, most visiting males originated there. When a female nested near the common boundary of one or more coteries, males from each visited. Visiting males tended to show a linear relation between rank in visiting activity and distance of their space of activity from a nest. The social system, in general, is complex and unlike any previously described for birds.

Although observations of early nests in the breeding period suggest synchrony between close females, analysis did not support widespread synchrony of reproductive activity within a colony.