vExtreme E Venezuela, Guyana, French Guiana, C Amazonian Brazil, E Ecuador, NE Peru, N Bolivia
1 Recognition tentative; see Cohn-Haft (1999) [Cohn-Haft, 1999 #1007] for remarks on geographic variation.
2 May deserve species rank (with subspecies chocoensis); see Meyer de Schauensee (1966) [Meyer de Schauensee, 1966 #2676], Whittaker & Oren (1999) [Whittaker, 1999 #14291], and Cohn-Haft (1999) [Cohn-Haft, 1999 #1007], but see also Holyoak (2001) [Holyoak, 2001 #1992].
3 For treatment as a separate species from N. griseus see Davis (1978) [Davis, 1978 #8923], Stiles & Skutch (1989) [Stiles, 1989 #13786], and Cohn-Haft (1999) [Cohn-Haft, 1999 #1007]. They form a superspecies (Cohn-Haft 1999) [Cohn-Haft, 1999 #1007], possibly also including N. maculosus, see Sibley & Monroe (1990) [Sibley, 1990 #3636].
4 For recognition see Cleere (1998) [Cleere, 1998 #988], but see also Cohn-Haft (1999) [Cohn-Haft, 1999 #1007].
5 Treated as a subspecies of N. griseus by Cleere (1998) [Cleere, 1998 #988], but transferred to this species by Cohn-Haft (1999) [Cohn-Haft, 1999 #1007], who also considered it doubtfully diagnosable.
6 May deserve species rank; see Cohn-Haft (1999) [Cohn-Haft, 1999 #1007].
7 Forms a superspecies with N. jamaicensis; see Cohn-Haft (1999) [Cohn-Haft, 1999 #1007].
8 Includes cornutus; see Holyoak (2001) [Holyoak, 2001 #1992].
9 For treatment as a separate species from N. leucopterus see Schulenberg et al. (1984) [Schulenberg, 1984 #3543].
10 May merit recognition of a monotypic genus (Costa & Donatelli 2009) [Costa, 2009 #11958].