Aulacorhynchus caeruleogularis - Blue-throated Toucanet

Skutch, A. F. 1944. Auk: 61(1): 61-88.
The Life-History of the Prong-Billed Barbet In his engaging prosaic style, the renowned naturalist, Alexander Skutch, proposes an evolutionary relationship between the Prong-billed Barbet (Dicrorhynchus frantzii) and the Blue-throated Toucanet (Aulacorhyncus caeruleogularis); natural selection may have permitted the barbet, with the uniquely defensive tunnel-doorway of its nest cavity, to better succeed than other birds, particularly woodpeckers, within the range of egg-predators like the toucanets. Additionally, and in passing, Skutch notes that among birds in which both sexes incubate, toucanets are less patient nest-sitters than barbets which are on the nest just more than nineteen hours a day. Finally, in this natural history of the barbet, Skutch notes, without detail, that the Blue-throated Toucanet prefers "hard fruits" to "soft fruits and fruit pulp".