Co-operative parental care; contribution of the male rifleman (Acanthisitta chloris) to the breeding effort

A colour-banded population of Riflemen at Kowhai Bush, Kaikoura, New Zealand was studied to determine the contribution of males to the care of young. Parental care and territorial behaviour were qualitatively the same throughout the breeding period. Males fed the females during courtship and in this way contributed the food required to produce the first clutch of eggs. Males made 66% of nest-building visits (early nests), spent 50% more time incubating than their mate by day (both clutches), leaving the females the thermo-insular advantage of incubating at night, always fed young significantly more often than their mate and contributed 55-77% of all food items fed to broods without helpers (the great majority of nests), and shared territorial defence equally with their mate. However, nest-building and territorial defence occupied less than 1% of parents’ time early in the breeding season. One widower was unable to fledge young alone. Early season sex ratios for the years studied were (M:F) 22:15, 50:35, 39:37 and 20:21 with extra males sometimes becoming helpers. The male’s high parental effort was not reflected in significantly lower survival to the next breeding season. Possible reasons for the large contribution by the male Rifleman to the breeding effort are discussed.