First observations of nest and nestling of the Black-cheeked Ant-Tanager Habia atrimaxillaris (Dwight & Griscom 1924), endemic to the Golfo Dulce rainforests, Costa Rica

A nest and nestlings of the endemic black-cheeked ant-tanager Habia atrimaxillaris were first found near the Tropenstation La Gamba, in SW Costa Rica, in February 2008. The nesting site is situated in the largely primary Esquinas forest near the Golfo Dulce, where H. atrimaxillaris is regularly observed. The nest and nestlings are described here in comparison with other Habia species. Aspects of breeding behaviour are discussed, including new findings such as the discovery that a non-breeding helper is involved in rearing the juveniles.