SUMMARYRecher, H. F. 1977. Ecology of co-existing White-cheeked and New Holland Honeyeaters. Emu 77: 136–142.The ecology and breeding biology of White-cheekedPhylidonyris nigraand New HollandP. novaehollandiaeHoneyeaters has been studied since 1967 in the Brisbane Waters National Park north of Sydney, NSW. This is an area where the ranges of the two birds overlap and in one study plot, a heath, both nest close to each other. Only the White-cheeked occurs in a second plot, a dry sclerophyll woodland, near the heath. Breeding bird censuses have revealed that during most years similar numbers of honeyeaters nest during the autumn and spring but there can be considerable variation in numbers between years. The number of nesting pairs may be related to weather and to long-term changes in vegetation but there is no consistent pattern and numbers may be determined by environmental factors outside the study area. Both species forage in similar ways and take insects and nectar from the same places. It is suggested that the presence of both on the heath for part of the year is related to the abundance of nectar. In other places where the species overlap they are separated by habitat. Data on clutch size, nest sites and breeding success are presented and discussed.