Black-spotted Piculet      Picumnus nigropunctatus
Zimmer-JT & Phelps, Sr.   1950
ne Venezuela: n,e Sucre to ne Monagas and Delta Amacuro. Humid lowland forest and edge
split from: Picumnus exilis
insert after: Picumnus exilis
H. Winkler & D.A. Christie,
Family Picidae (Woodpeckers), p. 296-555, in: Handbook of the Birds of the World. Vol. 7, J. del Hoyo, A. Elliott & J. Sargatal (eds.), Barcelona, 2002
 

American Three-toed Woodpecker     Picoides dorsalis
Baird  1858
U.S.A.: Alaska, Washington, Oregon, Rockies s to c Arizona & sc New Mexico, ne Minnesota e to n New England; Canada: Yukon, British Columbia e to Newfoundland
split from: Picoides tridactylus
insert after: Picoides tridactylus
Robert M. Zink, Sievert Rohwer, Alexander V. Andreev & Donna L. Dittmann,
Trans-Beringia comparisons of mitochondrial DNA differentiation in birds
The Condor 97 (1995): 639-649 

Caatinga Woodpecker is known from a single specimen, (an adult female) collected in 1926 by E. Kaempfer.   It is deposited in the American Musueum of Natural History, where Charles O'Brien noticed its unusual plumage first.  After he retired, Short continued the investigation, and eventually described it as a subspecies of C. spectabilis in 1973.
Despite searches by Novaes in 1980, it has not been seen since collection of the holotype.

Whittaker & Oren note that the type locality is 3,150 km east of the known range of C. spectabilis and the habitat is dry cerrado mixed with caatinga.  C. spectabilis is usually found in bamboo. The type locality is a region of high endemism. Because of the geographical separation, different habitat requirements and the plumage and size differences they suggest Celeus obrieni should be considered a full species.

Caatinga Woodpecker     Celeus obrieni
Short-LL   1973
ne Brazil: w Piauí, near Uruçuí on the Rio Parnaíba
split from: Celeus spectabilis
insert after: Celeus spectabilis
Andrew Whittaker & D.C. Oren,
Important ornithological records from the Rio Juruá, western Amazonia, including twelve additions to the Brazilian avifauna
Bulletin B.O.C. 119. 4 (1999): 235-260