The Yellow-rumped Thornbill often associates with other insectivorous species, such as other thornbills, fairy-wrens and robins. These mixed-species feeding flocks move through the landscape, foraging on the ground or among woody debris as they go. Thornbills also unwittingly associate with cuckoos, smaller species of which often parasitise them. Breeding Yellow-rumped Thornbills usually incorporate a ‘false nest’ on top of their bulky, domed nests, and it is sometimes suggested that this is to combat the threat of parasitism by cuckoos. Despite this, the nests are often parasitised anyway.