AMERICAN MUSEUM NOVITATES Published by Number 1168 the AMERICAN MUSEUM of NATURAL HISTORY April 21, 1942 New York City
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AMERICAN MUSEUM NOVITATES Published by Number 1168 THE AMERICAN MUSEUM OF NATURAL HISTORY April 21, 1942 New York City STUDIES OF PERUVIAV BIRDS. NO. XLII' THE GENUS POLIOPTILA BY JOHN T. ZIMMER As in other papers of this series, names of I believe, therefore, that superciliaris is colors are capitalized when direct compari- a recognizable form, ranging from the Canal son has been made with Ridgway's "Color Zone to Guatemala. I am unable to Standards and Color Nomenclature." separate "magna" of Ridgway from Costa Rica, which I find to fall within the limits Polioptila plumbea bilineata (Bonaparte) of variation of superciliaris. (Culicivora) bilineata BONAPARTE (ex LICHTEN- In this connection, I find myself unable sTEIN MS.), 1860, Consp. Av., I, p. 316-Carth- to agree with Hellmayr who placed albiloris agena, Colombia; cotypes in Berlin Mus. and "bairdi" in the same species with A long series of birds from various parts bilineata and commented on certain ex- of Central America is sufficiently distinct amples which he considered intermediate from South American specimens to raise between the two groups. The distinctions the question, once again, of the validity between the two groups are no greater than of superciliaris and magna as separable those which separate certain of the con- forms. The birds from Central America species of bilineata from each other, and have the lateral under parts quite notice- the specific association of albiloris with the ably darker and grayer than the South same forms would be strongly suggested American examples of bilineata, and the except for an apparent conflict of ranges gray of the back averages a little darker, that appears in the material at hand. though not as pronouncedly as the tone There is more than the matter of the of the under parts. This contrast is not extent of the white feathering in the loral shown merely by a few examples but is and superciliary regions to distinguish observable in almost all of over one albiloris and superciliaris. In albiloris hundred and thirty skins, about evenly there is a marked seasonal difference in divided between the two areas. There the development of white in this region also is a certain average difference of size, (as elaborated by Van Rossem, 1931, Auk, although there is too much overlap to XLVIII, p. 35), but in superciliaris there permit this character to be used alone. is no such seasonal difference, although Twenty-one adult males from South there is a sexual difference of the same sort America have the tail 41-47 mm. in length in one of the conspecies of this form (cf. (av., 43.5); twenty-seven adult males discussion of P. pl. major). Albiloris is from Central America have the tail 36-43 somewhat larger than superciliaris. Ex- mm. (av., 40). Some South American cluding southwest-Mexican birds, of which examples have a certain amount of grayish more will be said below, twenty-three adult shading on the lateral under parts, but it males have the tail 42.1-48.2 mm. in is of a lighter tone than that of the Central length (av., 45.5). It is decidedly more American birds. In series, the distinctions purely whitish below, without the gray are pronounced. tones of superciliaris, or at least with much 1 Earlier papers in this series comprise American paler gray shading. The black areas at Museum Novitates, Nos. 500, 509, 523, 524, 538, 545, 558, 584, 646, 647, 668, 703, 728, 753, 756, 757, the bases of the outer rectrices are notice- 785, 819, 860, 861, 862, 889, 893, 894, 917, 930, 962, ably more extensive than in superciliaris 963, 994, 1042, 1043, 1044, 1045, 1066, 1095, 1108, 1109, 1126, 1127, 1159, and 1160. (most easily compared on the subexternal 2 AMERICAN MUSEUM NOVITATES [No. 1168 rectrix), and the pale outer border of the the largest of the series. The lengths of larger tertials is broader, more sharply tail in the adult males from different defined and often more purely white. The regions are as follows: W. Mexico (4 top of the head in the adult males is more skins), 48-51 mm. (av., 49.6); W. Honduras bluish and more highly glossy. (6), 44-48 (av., 46.1); C. Guatemala (5), These characters appear together in the 42-46 (av., 44.9); Nicaragua (5), 42-48 specimens examined, and I am unable to (av., 44.8); Costa Rica (7), 44-48.2 (av., find a single example that is not readily 45.9). assignable to one form or the other. Even Ridgway (1904, Bull. U. S. Nat. Mus., using only the broad, full superciliary of L, pt. 3, pp. 725, 726) restricted albiloris to superciliaris as a single criterion, there ap- Guatemala and Oaxaca, Mexico; bairdi, pears to be positive demarcation, and I to Nicaragua and Costa Rica. He found have seen no specimen of albiloris with male albiloris (all from Oaxaca) to have the more than a thin line above the orbit. tail 49-56 mm. (av., 52.6), but Van Ros- With this segregation of characters, I sem (loc. cit.) included all west-Mexican have specimens of both forms from Bebe- birds of this group in "bairdi" with an dero, Costa Rica, and the vicinities of average tail-length (males) of only 48 mm. Matagalpa and Chinandega, Nicaragua. Obviously there is much work still to be A series of albiloris from Progreso, Guate- done on the variations and distinctions in mala, is from the eastern side of the water- the albiloris group, and it appears probable shed, while the specimens of superciliaris that there is a large form in western Mexico from the same country are also from the still to be characterized and named. I do east, although nearer the coast and in a not see how it can be referred to "bairdi" less arid region than Progreso. Possibly or how a "bairdi," based on Nicaraguan the distributional segregation of the two birds, can be distinguished from albiloris. forms throughout their ranges is more a Returning to the consideration of P. matter of ecology than simple geography. plumbea bilineata, I must say that I have Nevertheless, the remainder of the two only one bird from Santa Marta to repre- series of these forms from northern Costa sent the north-Colombian population of Rica, Nicaragua, and Honduras are from the subspecies, in this case the population opposite sides of the cordillera. In south- to which the name bilineata adheres. This ern Costa Rica, superciliaris occupies both single bird agrees in coloration with the sides of the mountains. On the other west-Ecuadorian and west-Peruvian birds, hand, albiventris, which I believe is to be although in size it can be matched in both considered as a form of albiloris, is found these and Central American skins of in northern Yucatan and on Cozumel superciliaris. In view of the approxima- Island, on the Caribbean side of Mexico, tion in color, therefore, I follow earlier in arid regions. authors in assigning the west-Ecuadorian I am unable to follow Van Rossem's and west-Peruvian birds to bilineata in distinctions between albloris and "bairdi" spite of the hiatus in distribution that (1931, Auk, XLVIII, pp. 34-39). He occurs in western Colombia where the gives the length of tail in albiloris as 53 form has not been found to date. mm., in "bairdi" as 48, and restricts As to the matter of specific association albiloris to eastern Guatemala and south- with plumbea, the case appears to be fairly ern Mexico on the Atlantic side of the clear. A male of plumbiceps from Honda, mountains (but without giving Mexican Colombia, shows decided, white lores and localities for this latter form). The sup- superciliaries, and another male from the posed "bairdi," described by Ridgway same locality has a lesser amount of white from Nicaragua, is said to be confined to in the same area, at the tips of the feathers. the Pacific drainage. A female from the foot of Mt. Duida has a My only Mexican birds of this species, very slight suggestion of white above the except the type of albiventris, are from the lores, and one from the upper Orinoco has Pacific side of Oaxaca, and these birds are traces of white above the eyes. The 1942] STUDIES OF PERUVIAN BIRDS. XLII 3 amount of white on the outer three rec- that this close approximation of the sexes trices varies sufficiently to show perfect would be a sufficiently distinctive character transition between plumbiceps and bilineata to serve as a basis for specific isolation of in this respect. General measurements maior, but there is much evidence to show good intergradation. In distribu- weaken this idea. tion there is no conffict. In this series of bilineata, parvirostris, The conclusion to be reached from this anteocularis, plumbea, and plumbiceps there evidence is that bilineata and its accepted are occasional specimens dressed in typical conspecies must be added to the plumbea female plumage except for their noticeably group through demonstrable relationship darker heads. These birds were marked to plumbiceps. by their collectors as females, and although In Perd, the range of bilineata is re- these determinations have been questioned stricted to the Pacific coast and western in one or two cases by subsequent workers, slopes of the western Andes from Pacas- I believe that the birds in question actually mayo north to the Ecuadorian boundary, are females and not young males as sug- thence extending northward to Esmeraldas, gested. A similar bird is the type of Ecuador. Peruvian records are from Pacas- plumbiceps which was sexed by the col- mayo, Tembladera, Guadalupe, and Lechu- lector as a male but which is rather gal, as well as the localities mentioned in exactly matched by other skins sexed as the subjoined list of material examined.