The Auk 121(4):1031–1039, 2004 A NEW SPECIES OF THAMNOPHILUS ANTSHRIKE (AVES: THAMNOPHILIDAE) FROM THE SERRA DO DIVISOR, ACRE, BRAZIL Bwjy M. Wmnyj,1,3 Df{ni C. Owj,2,4 fi Rtgg T. Bwrknji1 1Museum of Natural Science, 119 Foster Hall, Louisiana State University, Baton Rouge, Louisiana 70803, USA; 2Departamento de Zoologia, Museu Paraense Emílio Goeldi, Caixa Postal 399, 66.017-970, Belém, Pará, Brazil Agxywfhy.—We describe a new species of Thamnophilus antshrike—T. divisorius (Acre Antshrike)—from the Serra do Divisor of Acre, Brazil. The new species is known from a single small ridge (though we expect that it is present on other, unexplored ridges in the Acre Arch uplands), and is common in the interior of shrubby woodlands on poor soil physiognomically similar to white-sand habitats in the Guianas and Amazonia. Thamnophilus divisorius is sister to T. insignis (Streak-backed Antshrike), a narrow endemic of pantepui, and forms a well- supported clade with that species and T. amazonicus (Amazonian Antshrike). Thamnophilus divisorius occurs in a remote region within a national park in Brazil; despite its limited range, we are optimistic about its future survival. Received 16 May 2003, accepted 24 June 2004. Rjxrt.— Descrevemos uma nova espécie de tamnofi lídeo (Thamnophilus divisorius, Choca- do-Acre) oriunda da serra do Divisor, Acre, Brasil. A nova espécie é conhecida de apenas um único cume de serra (embora é esperada existir em outras áreas similares ainda não pesquisa- das nos arredores), e é comúm no interior de bosques de vegetação baixa crescendo em solos pobres que lembram habitats de campina de areia branca e vegetações afi ns nos Guianas e na Amazônia. É fi logeneticamente mais próximo de Thamnophilus insignis (Choca-de-Roraima), espécie de distribuição restrita à região de pantepui, e forma um clade com Thamnophilus amazonicus (Choca-canela). Thamnophilus divisorius ocorre numa região remota dentro de um parque nacional e, apesar de ter uma distribuição extremamente restrita, estamos otimistas sobre a sua sobrevivência no futuro. I J 1996, the fi eld phase of a manage- inventory; B.M.W., D.C.O., and the technician ment plan for the Parque Nacional da Serra D. C. Pimentel Neto conducted the fi eld work. do Divisor (PNSD) in Acre, Brazil, was initi- Although the fi rst phase encompassed only 18 ated. The project was funded by The Nature fi eld days, with observations divided among Conservancy International of Alexandria, six sites in the northern sector of the park, we Virginia, and coordinated in Brazil by the documented several species of birds previously national offi ce of The Nature Conservancy in unknown or poorly known in Brazil, including Brasília, D.F., the nongovernmental organiza- a striking Thamnophilus antshrike new to sci- tion S.O.S. Amazônia in Rio Branco, Acre, and ence, which we propose to name: the national and regional offi ces of the Instituto Brasileiro do Meio Ambiente e dos Recursos Thamnophilus divisorius sp. nov. Naturais Renováveis (IBAMA). One key aspect Acre Antshrike of the project was a rapid ecological evaluation Choca-do-Acre (Portuguese) (REA; Sobrevila and Bath 1992) of the park’s fl ora and fauna. The ornithology section of Holotype.—MPEG no. 52754; adult male, the Museu Paraense Emílio Goeldi (MPEG) in from Morro Queimado, in the Serra da Belém, Pará, was responsible for the avifaunal Jaquirana (one of the easternmost ridges in the Serra do Divisor), above the leV bank of the rio Moa in Parque Nacional da Serra do 3E-mail: [email protected] 4 Divisor, Municipality of Mâncio Lima, Acre, Present address: Conservation Priorities Coor- ∼ dinator, The Nature Conservancy, Eastern South Brazil (07°26’36”S, 73°40’28”W); 500 m; col- America Division, SHIN Centro de Atividades 05 lected 10 July 1996 by B.M.W., prepared by D. Conjunto J Bloco B, 3o Andar, 71.503-505 Brasília, D.F., C. Pimentel Neto. Tape-recorded by B.M.W., Brazil. Macaulay Library of Natural Sounds (MLNS), 1031 1032 Wmnyj, Owj, fi Bwrknji [Auk, Vol. 121 Cornell Laboratory of Ornithology, Ithaca, oV en the penultimate note, is louder, longer, and New York, no. 79060; Arquivo Sonoro Elias P. of slightly higher peak frequency than the rest Coelho (ASEC), Universidade Federal do Rio de of the series, but does not diff er dramatically in Janeiro, Rio de Janeiro, Brazil, no. BMW 054/10; structure or tonality. Recorded calls appear to be and Isler inventory, Alexandria, Virginia, no. less clearly diff erentiated from those of several BMW.125:21. other Thamnophilus species. Diagnosis: Morphology.—Allocation of the new Distribution.—Known only from the type species to the genus Thamnophilus is diffi cult to locality, the new species probably occurs on justify objectively on the basis of morphology, other, physiognomically similar ridges in the because characters of diagnostic value have not Acre (sometimes called Serra do Moa) Arch been identifi ed for the genus and because the uplands in the Serra do Divisor of Acre, perhaps present group of ∼25 species (as currently classi- extending to the continuous Sierra Contamana fi ed) may not be monophyletic. The type species in Ucayali, Peru (Fig. 1). of Thamnophilus is T. doliatus (Barred Antshrike), Description of holotype.—(See cover plate.) which is barred black-and-white in the male Alphanumeric color designations were deter- plumage, and mostly rufous-brown in the mined from direct comparison with the Munsell female plumage. These factors notwithstanding, (1994) soil color chart. Crown from base of bill the new species is most similar morphologically to nape semi-glossy black with a few sca ered to members of Thamnophilus. Adult males are albino feathers in forehead and occipital–nuchal readily distinguished from other Thamnophilus regions; not crested. Sides of head and neck species by a combination of the following a fl a er black, less intense and lacking gloss. characters: entirely dark-bluish-gray plumage Feathers of back and scapulars same black as with somewhat blacker hood, wings, and tail, sides of head, widely margined with subtly paler and mo led grayish (rather than mostly white) bluish black (nearest Gley 2, 2.5/1/5PB), impart- underwing coverts. Adult females diff er distinc- ing a weakly mo led eff ect, which is seen to tively from other Thamnophilus species in hav- vary with viewing angle. Rump and uppertail ing almost uniformly bluish-gray facial region coverts dark bluish gray (Gley 2, 3/1/5PB). No and upperparts with slightly darker wings and white interscapular patch; those feathers instead tail, and entirely brownish-orange underparts. dull grayish. Throat subtly grayer than sides of Both sexes may show minute pale spots (white head but darker than remainder of underparts, in male, buff -orange in female) at tips of some which—together with black head and neck upperwing coverts; both sexes have small but region—contributes to a weakly hooded eff ect. more conspicuous spots at the tips of the outer Underparts from breast to undertail coverts, two rectrices; those are reduced to fringes or are including elongated, loosely integrated fl ank absent on the next one or two rectrices. feathers, uniform dark bluish gray, concolor Diagnosis: Voice.—The loudsong (following with rump. Upperwing coverts and tertials Willis 1967) of T. divisorius is similar in pa ern, same semiglossy black as crown. Tiny feathers at structure, and auditory quality to that of T. base of outer primary whitish; feathers at bend doliatus (especially the nominate form), which of wing mixed gray and whitish. Underwing aligns T. divisorius more objectively with the coverts with gray centers and whitish tips, genus Thamnophilus than does its morphology. or a single, whitish, internal band encircling That alignment is supported anecdotally: on the gray center, producing a mo led appearance. morning of its discovery, T. divisorius was heard Primaries blackish, subtly paler on outer edges and tape-recorded by B.M.W. for nearly an hour (visible on folded wing), all except outermost before being seen, and it was clear from its song with contrasting wide silvery-white margins that it was an unnamed Thamnophilus antshrike. 1–2 mm on inner webs, especially visible on ven- Thamnophilus divisorius‘ loudsong diff ers from tral surface, those margins becoming progres- the song of all other Thamnophilus species by the sively more extensive from outermost primary following combination of characteristics: (1) it (which is shorter and wholly blackish) to inner- accelerates in pace (progressively shorter inter- most. Tail graduated, same semiglossy black as note intervals) for approximately half its dura- crown and upperwing coverts. Outermost rectrix tion, slowing slightly and gradually through the with white tip 1.5 mm wide, extending to both fi nal two or three notes; (2) its terminal note, and webs; tips present but decreasing in size on next October 2004] New Antshrike from Acre, Brazil 1033 Fnl. 1. Composite LANDSAT image of the northern half of Parque Nacional da Serra do Divisor (white out- line), Acre, Brazil. The single confirmed locality of Thamnophilus divisorius, “Morro Quiemado,” is indicated by an × ; it is slightly north of the Rio Moa in the Serra da Jaquirana. The view from the ridge, looking northwest, is shown in Figure 2. The ridge system comprising the Acre Arch uplands appears as a textured band running northwest into Ucayali, Peru; a somewhat disjunct system south of the Moa appears to be lower in relief. These areas are virtually unexplored biologically. We expect that T. divisorius will eventually be found on most, per- haps all, of the higher ridges in the region. three pairs of rectrices; two central pairs with Description of allotype.—(See cover plate.) worn tips but apparently lacking any white.