No. 10. — The Ornithology of Guerrero, Mexico By Ludlow Griscom Ornithologists have long known that the State of Guerrero was one of the richest sections of Mexico, which would well repay further investigation. The hot Pacific lowlands are a part of the very distinct fauna closely related to the Central American Arid Tropical Fauna. The lofty Sierra Madre del Sur almost bisects the State into a northern and southern half. It is remarkable for being the meeting ground of three different faunas. Most important of all, perhaps, this mountain range is the northernmost outpost, on the western side of the continent, of the Subtropical Zone of Central America and the Andes. It also proves to be the southern limit of various boreal, Rocky Mountain, or Upper Sonoran types. Finally the many birds characteristic of the table-land of Mexico reach these mountains as one of their western or southwesternmost outposts. These factors combined result in a remarkable assemblage of endemic species and subspecies, and every competent collection made there has yielded a rich harvest of new forms. The Museum of Comparative Zoology was accordingly fortunate in securing the services of the veteran collector W. W. Brown, who happened to be in Mexico City early in 1930 on a free lance expedition. With some difficulty he was persuaded to collect in Guerrero, reached that State in early October and remained until June, 1932. The first six months were spent in the lowlands on both sides of the mountains, and the final year in the mountains around Chilpancingo. Unfortun-ately Mr. Brown never really collected in high cloud forest, but his collection gained in the thoroughness with which the high pine and oak woods were combed, as the results recorded beyond amply prove. We accordingly purchased his entire Guerrero collection, slightly over 1,500 specimens. His itinerary was as follows: — Taxco. A large town northwest of Iguala. Oct. 9-Nov. 1, 1930 and Nov. 10-15, 1930. Iguala. A town on the railroad south of Cuernavaca in Morelos, and well north of the Sierra Madre. Altitude about 3,000 ft. Nov. 5, 1930. Cacalatenango. A hamlet in the immediate vicinity of Iguala. Nov. 10 and 11, 1930.