Systematic notes on the bird family Cracidae. No. 2, Relationships and geographical variation of Ortalis vetula, Ortalis poliocephala, and Ortalis leucogastra. American Museum novitates ; no. 2222
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Date
1965
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New York, N.Y. : American Museum of Natural History
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Abstract
"The chachalacas of Mexico belong to three species: Ortalis vetula Wagler, which ranges from the lower Rio Grande Valley southward through eastern and southern Mexico to Honduras, including the island of Utila, and northwestern Nicaragua, occurring again in Guanacaste in northwestern Costa Rica; O. poliocephala Wagler, which ranges from southern Sonora southward through western Mexico to the region of Pijijiapan in coastal Chiapas; and O. leucogastra Gould, which ranges from Pijijiapan southward in the coastal districts of the Pacific to northern Nicaragua. The three were considered to be conspecific by all authors until Moore and Medina (1957) stated that vetula and poliocephala, and probably leucogastra also, were separate species. The present paper confirms the opinion of Moore and Medina. It discusses the relationship of the three species and suggests that the nearest relatives of leucogastra are probably not vetula and poliocephala but a group of South American species (superciliaris, motmot, and guttata) with which it shares a morphological character that appears to be of phylogenetic importance in the genus Ortalis, namely, the structure and color pattern of the feathers of the breast. The three species of Mexico are mainly geographical representatives, and their distribution in Mexico is discussed in detail, showing that the ranges of vetula and poliocephala meet and overlap slightly on the Isthmus of Tehuantepec, and that the ranges of all three species meet and probably overlap in the region of Pijijiapan in coastal Chiapas. The morphological characters and the vocalizations of the three species are analyzed. The morphological characters of the three species, and the vocalizations of vetula and poliocephala, are very distinct. The evidence concerning the vocalizations of leucogastra is inconclusive for technical reasons. It is suggested that differences in vocalizations may be the most important isolating mechanism in Ortalis. The geographical variation is discussed. Ortalis leucogastra does not appear to vary geographically. Ortalis poliocephala consists of two subspecies (wagleri Gray, in the north of the range south to Jalisco, and nominate poliocephala south of wagleri); wagleri differs strikingly from nominate poliocephala by being chestnut, as against white, below the breast, and this difference was universally considered to be of specific importance until Moore and Medina (1957) reported that the two birds interbreed in western Jalisco. The geographical variation of vetula is relatively slight and is clinal in some regions. In these and northern Yucatan, the degree of color saturation seems to be correlated with annual rainfall, but beyond a certain critical point (apparently around 1500 mm. of rain) the coloration is no longer correlated with humidity. Four subspecies are recognized in vetula: mccalli Baird, ranging from the Rio Grande Valley to northern Veracruz and southeastern San Luis Potosi; pallidiventris Ridgway, in the northern arid Yucatan Peninsula; deschauenseei Bond, on Utila Island; and nominate vetula in the rest of the range. Among the forms synonymized with nominate vetula is intermedia Peters, on the ground that this form represents morphologically unstable populations from a zone of intergradation between pallidiventris and nominate vetula"--P. 31-32.
Description
36 p. : ill., maps ; 24 cm.
Includes bibliographical references (p. 34-36).
Includes bibliographical references (p. 34-36).
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