The red-faced sturdybill (Robustirhynchinis rubicundis) is a common denizen of the lowland forests of New Guinea, where it subsists upon fruit and nectar from flowers.

    These birds habitually make their homes in the large, tower-like nest of the architect ant (Architecton affabre), a common insect across Australasia.  Normally, these ants are fiercely protective of their nests, ripping any intruder apart with powerful mandibles.  However, the sturdybills may come and go from the nest's upper chambers completely unmolested.  Analysis has proven that the birds secrete a a complex series of pheromones on their feathers, masking their presence from the ants.  The sturdybills, in return for the scraps of fruit and leaves they pile within the nest, receive the protection of a virtually impenetrable fortress, with the added bonus of being constantly cleaned of lice and other external parasites by the roving ants.  The relationship between these two species, therefore, is rather one-sided, with the birds receiving most of the benefits, but the ants do not seem perturbed by their giant neighbors.