126 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



YERMIVORA CRISSALIS (Salvin and Godman) 



COLIMA WARBLER 



CONTBIBUTED BY JOSSELYN VaN TYNE 



HABITS 



Described in 1889 from a single specimen collected by W. B. Kicli- 

 ardson in the Sierra Nevada de Colima, Mexico, this handsome warbler 

 was, in 1932, still known from only a dozen museum specimens, and 

 not a word had been recorded on its habits. In that year a University 

 of Michigan expedition found the Colima warbler to be common in 

 the higher forests of the Chisos Mountains of southwestern Texas and 

 made the first discovery of its nest and eggs. The basis for the inclu- 

 sion of this warbler in the A.O.U. Check-List had been a single 

 specimen collected by Frederick M. Gaige in the Chisos in 1928 (Van 

 Tyne, 1929). 



The range of the Colima warbler has been recorded only very 

 sketchily, but Bangs (1925) was probably correct in surmising that 

 the specimens from southern Mexico (Colima and Michoacan) were 

 migrant birds. The closely related Virginia's warbler, which nests 

 in the Rocky Mountain States, winters mainly in Michoacan, Guerrero, 

 and Jalisco. Recently R. T. Moore (1942) added a second, more 

 southerly, locality in Michoacan and one in eastern Sinaloa to the 

 known southern range of the Colima warbler. The breeding range 

 is apparently restricted to the highlands of northeastern Mexico and 

 the Chisos Mountains of southwestern Texas. In Texas the Colima 

 warbler occurs at altitudes between 6,000 and 7,500 feet (Van Tyne, 

 1936) ; in Coahuila, apparently, only above altitudes of approximately 

 7,500 feet (Burleigh and Lowery, 1942). Records from the southern 

 part of its range, however, show a greater altitudinal spread. The 

 type specimen was taken in Colima at about 8,000 feet, and R. T. 

 Moore (1942) reports two November specimens, one taken at 9,500 

 feet in northeastern Michoacan, the other at 5,200 feet in Sinaloa. 

 These represent the extremes of the known altitudinal range. 



Courtship. — Mating behavior has been observed during the first few 

 days of May and sets of eggs noted May 15 (just completed) and May 

 20 (highly incubated). The only recorded specimen in juvenal plum- 

 age was collected July 20. Peet observed pursuit behavior in the 

 Chisos Mountains on May 4 (within a few days of nest building), 

 which may have had some courtship significance, but nothing definite 

 is known of the courtship habits. Sutton noted copulation twice on 

 May 1 in the Chisos, and the gonads of specimens collected that day 

 were much enlarged; there was no indication that the females had 

 begun incubating. 



