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.'ROBERT'__K. SELANDER AND DONALD R. GILLER BULLETIN OF-THE AMERICAN MUSEUM OF-NATURAL HISTORYi VOLUME 124,:ARTICLE 6NEWV YORK: 1963 SPECIES LIMITS IN THE WOODPECKER GENUS CENTURUS (AVES) SPECIES LIMITS IN THE WOODPECKER GENUS CENTURUS (AVES) ROBERT K. SELANDER Research Fellow, 1961, Department of Ornithology The American Museum of Natural History Associate Professor, The University of Texas Austin, Texas DONALD R. GILLER Graduate Student, Department of Zoology The University of Texas Austin, Texas BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 124 : ARTICLE 6 NEW YORK 1963 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Volume 124, article 6, pages 213-274, text figures 1-17, plates 53-56, tables 1-8 Issued March 4, 1963 Price: $1.50 a copy INTRODUCTION THE PRINCIPAL OBJECTIVE of the present FIELD WORK AND MATERIALS study was to ascertain the systematic rela- tionships among populations of woodpeckers Field work was undertaken in M6xico in of the genus Centurus occurring in the United June and July, 1958, for the primary purpose States, Mexico, and northern Central Amer- of studying the relationship of Centurus auri- ica. Because the distributional pattern of frons and C. uropygialis in Aguascalientes and species of this complex is strongly allopatric Jalisco; but some time was devoted to C. and the morphologic criterion of relation- chrysogenys in Colima and Nayarit, C. hypo- ship is notably unreliable, considerable con- polius in Puebla, and C. aurifrons in Coa- troversy as to species limits has developed huila, San Luis Potosi, and Tamaulipas. Our among taxonomists working with museum investigations are based on 231 specimens specimens alone. But recent field investiga- collected in Mexico in 1958, all of which have tions in zones of contact between allopatric or been deposited in the American Museum of narrowly sympatric forms, together with Natural History, and on material obtained on analyses of morphologic variation in speci- loan from the following institutions: mens, have yielded important information The American Museum of Natural History that contributes to our understanding of (A.M.N.H.), through the courtesy of Dr. systematic relationships within the genus. Dean Amadon and Mr. C. E. O'Brien; British The present report is primarily concerned Museum (Natural History) (B.M.N.H.), with species of Centurus occurring in the through Dr. R. W. Sims; Chicago Natural United States and in northern and central History Museum (C.N.H.M.), through Dr. Mexico, namely, C. carolinus, C. aurifrons, C. M. E. Traylor; Donald Dickey Collection uropygialis, C. hypopolius, and C. chryso- (University of California, Los Angeles) genys; but, in addition, we have treated C. (D. C.), through Dr. T. R. Howell; Museum hoffmanni of Costa Rica and Nicaragua and of Zoology, Louisiana State University have included systematic comments on sev- (M.Z.L.S.U.), through Dr. R. J. Newman; eral other forms referred to the genus. The Museum of Zoology, University of Michigan geographic distribution of species considered (M.Z.U.M.), through Dr. R. W. Storer; in detail in this report is indicated in figure 1, Museum of Vertebrate Zoology, University of and specimens of several species are shown in California, Berkeley (M.V.Z.), through Dr. plates 53 to 55. A. S. Leopold and Dr. F. A. Pitelka; and Research on Centurus was supported by the United States National Museum (U.S.N.M.), National Science Foundation (Grant 3448) through Dr. H. Friedmann. and the Research Institute of the University In addition, specimens in the Museum of of Texas (Grant URI-871). The study was Comparative Zoology, Harvard University, completed in 1960, while the senior author and the Peabody Museum, Yale University, was a Research Fellow in the Department of were examined in October, 1960, through the Ornithology of the American Museum of courtesy of Mr. J. C. Greenway, Jr., and Dr. Natural History. S. D. Ripley, respectively. 217 i ) ill I.."I I, L.% 0a} c)Io 04C) 0 a)U) en 04 *wn 0 0U) *I- 04 ,04.4 GENERIC LIMITS THERE IS LITTLEAGREEMENTamOng systemat- TABLE 1 ists as to the number of genera in which WING/TAIL RATIOS IN MALES of Centurus species of the Centurus-Tripsurus-Melanerpes complex are to be included. In many early Population Wing/Tail' classifications, as well as in some of recent date (Todd, 1946), three genera are main- C. hoffmanni 2.03 tained, but Peters (1948) has lumped all three C. aurifrons santacruzi under the name Melanerpes. Other workers SE. Honduras-Nicaragua have recognized two genera, combining Trip- (33)b 1.68 surus with Centurus (Mexican Check-List El Salvador (32) 1.75 Committee, 1957, p. 36) but maintaining NW. Honduras (31) 1.76 S. Guatemala (30) 1.82 Melanerpes, and still others (e.g., Wetmore, Central Guatemala (29) 1.76 1957, p. 51) unite Tripsurus and Melanerpes SE. Chiapas (22) 1.77 but regard Centurus as distinct. Mean, samples 22, 29-33 1.76 In the generic diagnoses of Tripsurus and C. aurifrons dubius Centurus prepared by Ridgway (1914), there Mean, samples 23, 25 1.65(1.62-1.69)0 is no character or combination of characters C. aurifrons grateloupensis providing clear distinction between the two Mean, samples 12, 15, 16 1.69(1.68-1.70) groups of species. The tail is supposedly two- C. aurifrons aurifrons thirds as long as the wing in Centurus and less Mean, samples 3, 5, 10, 14 1.71(1.69-1.75) than one-half as long in Tripsurus, but, in C. aurifrons polygrammus fact, the tail is slightly less than one-half as Mean, samples 18-21 1.74(1.67-1.85) C. carolinus (Texas) 1.64 long as the wing in C. hoffmanni and C. rubri- C. uropygialis capillus; and it is slightly more than one-half Sonora 1.58 as long in T. pucherani (see table 1). The Nayarit-Sinaloa 1.60 extent of feathering of the orbital region is Jalisco-Aguascalientes 1.63 another feature purportedly distinguishing Zacatecas 1.70 the two groups: in Tripsurus this region is C. hypopolius (Puebla) 1.56 bare, and in species of Centurus it is suppos- C. chrysogenys (Nayarit) 1.71 edly well feathered. However, as acknowl- C. pygmaeus edged by Ridgway himself, this region is fully Yucatfin 1.70 as bare in C. chrysogenys as in T. pucherani. Cozumel Island 1.62 in Bonaca Island 1.72 Moreover, it is almost as extensively bare C. rubricapillus C. rubricapillus and C. superciliaris, and an Panami 2.11 intermediate condition is seen in C. hypopo- Isla El Rey 2.12 lius. Similarly, the structure of feathers of the C. pucherani (Nicaragua) 1.92 malar apex is variable in both genera and C. chrysauchen (Costa Rica) 2.04 cannot serve as a diagnostic character. Nor do the shape and size of the nostril (sup- a Calculated from mean wing and tail lengths of posedly broadly oval in Centurus and oval or samples. ovate and smaller in Tripsurus) provide a b Numbers in parentheses refer to sample areas in- dicated in figure 2. basis for separation. a Wetmore (1957) argues for the mainte- Range. nance of Centurus as a genus distinct from pes. He fails, however, to point out that these Melanerpes (in which he apparently includes characters will not permit separation of Trip- Tripsurus) on the basis that the regularly surus and Centurus. barred back and the soft and "blended" In urging that "such apparently well- breast feathers of Centurus contrast with the characterized groups" as Centurus and Trip- uniformly colored back and the hair-like surus should not be combined with Melaner- feathers of the breast in "typical" Melaner- pes, Todd (1946, p. 297) suggests that "more 219 220 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY VOL. 124 weight should be given to color pattern." But that (1) both the adult male and female usu- when we compare the species assigned to ally sleep in the nest with their eggs or young Centurus and to Tripsurus, it is soon apparent (rarely roosting alone in separate cavities); that similarities in color and pattern between (2) the nest is kept clean until the young take Centurus chrysogenys and Tripsurus pucherani wing and later; and (3) fledglings return to actually provide the strongest argument for roost in the nest cavity with their parents and combining the two nominal genera. Speci- may continue this habit until the approach of mens of these two woodpeckers are shown in the next breeding season. plate 54. Similar features are: (1) dorsal bar- Although Skutch's observations are of con- ring of black and white; (2) extensive black siderable interest and should be extended to on side of head (in males of C. chrysogenys other woodpecker species, there is reason to this color is limited to the superciliary region, doubt that the reported differences in life whereas it also extends over the postorbital history of Central and South American spe- region in T. pucherani; in females of both cies of Tripsurus and Centurus are in any species, the black passes over the occipital sense "fundamental" or of unusual signifi- region as a band, which is wider in Trip- cance from a systematic standpoint. Also, we surus); (3) yellow frontal region; (4) naked, call attention to the fact that Skutch's con- black orbital region; (5) dark breast and clusions in regard to generic classification throat; and (6) barred flanks, the bars being were based on observations of only a few darker and more extensively distributed individuals representing less than half of the anteriorly in Tripsurus. total number of species assigned to these The chief difference in color between these genera. Hence, the degree of constancy of species involves the presence of yellow on the these differences in the two groups of species malar region and chin in C.

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