The trumpeters Psophia (Psophiidae) are three species of chicken-sized gruiform bird found in the Amazon and Orinoco rain forests in South America, named after their conspicuously loud calls.
In common with many other South American endemic groups, their appearance varies between the major Amazon river basins which first formed about three million years ago. This has led to vertying degrees of speciation and differentiation maintained by the relative permanency of the major zones and the inability of many birds to cross the huge rivers to exchange genes.
All three traditional species of trumpeter appear to have recognised subspecies now known to have diverged to species level under these fairly ideal conditions. Oppenheimer and Silveira (2009) worked on Dark-winged Trumpeter and concluded that there were probably three species involved in the complex: Psophia viridis from the Madeira-Tapajós interfluvial zone, P dextralis, found in the Tapajós-Tocantins interfluvium, and P obscura, which found on the right bank of the Tocantins River to the west of the State of Maranhão.
Ribas et al (2011) have now split most of the named trumpeter subspecies as morphologically distinct full species under the same principle; these correlate with all nine generally accepted geographical areas of Amazonian endemism, with only Grey-winged Trumpeter P crepitans inhabiting two such zones. They consider all eight lineages to be monophyletic (that is, they each contain all the descendants of one ancestor) with no overlap, and all appear to be diagnosable by plumage.
The splits are as follows: Napo Trumpeter P napensis from Grey-winged; Ochre-winged Trumpeter, P ochroptera, and White-winged Trumpeter, P leucoptera from Pale-winged Trumpeter sensu lato; and P interjecta, P dextralis, Green-winged Trumpeter, P viridis, and Dusky Trumpeter, P obscura from Dark-winged Trumpeter sensu lato (English names taken from Taxonomy in Flux). All except P interjecta and P dextralis appear to be reaching a reasonable consensus of acceptance by taxonomists - these two have not yet been freed from the possibility of hybridisation asserted by earlier workers.
Oppenheimer and Silveira. 2009. A taxonomic review of the Dark-winged Trumpeter Psophia viridis (Aves: Gruiformes: Psophiidae). Papéis Avulsos de Zoologia 49: 547-555.
Ribas, C C, Afonso, A A, Nogueira, C R, Miyaki, C Y and Cracraft, J. 2011. A palaeobiogeographic model for biotic diversification within Amazonia over the past three million years. Proceedings of the Royal Society B 10.1098/rspb.2011.1120