128 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



Egg laying, in the one instance observed, was at daily intervals 

 (May 12-15) ; the first egg was laid four days after completion of 

 the nest. Incubation had begun May 16, the day after the last egg 

 was laid. The length of the incubation period is not known. Females 

 collected on May 12 (Peet) , May 17 (Van Tyne) , and May 20 (Sutton) 

 had well-marked incubation patches ; males collected at the same time 

 had no patch. 



Plumages. — The Colima warbler differs from its nearest relative, 

 the Virginia's warbler, in being larger; darker, less gray, above; 

 crown paler ; rump and upper tail coverts darker and richer in color ; 

 yellow of throat and breast absent or, if present, more green and 

 more diffuse ; sides and flanks more brownish ; crissum darker, more 

 aniline yellow; sexes much more nearly alike. The adult female 

 Colima warbler is slightly darker than the male and is more brown 

 below. It is apparently never yellow on the breast. 



The Juvenal plumage (known from only one specimen) differs from 

 the adult plumage in lacking the crown spot and in having two buffy 

 wing bars. The rump is also much more yellow (less green) and the 

 crissum is more yellow (less orange). The young Colima warbler 

 differs from the young Virginia's warbler in having a larger bill 

 darker plumage, and a less ochraceous rump. 



The fall plumage differs from that of the spring in being "darker 

 and browner throughout, the gray of head a good deal obscured by 

 deep olive or light brownish olive; crown patch orange rufous; under 

 parts darker with whitish area in middle of belly more distinct and 

 under tailcoverts duller, more nearly aniline yellow" (Bangs, 1925). 



George Miksch Sutton's fine color plate (Van Tyne, 1936, frontis- 

 piece) of the Colima warbler is apparently the only published figure 

 of the species. 



Behavior. — In Texas, the Colima warbler was observed feeding on 

 insects (which were not identified), but nothing further has been re- 

 corded about its food. All observers seem to agree that it is not a 

 phy bird, although in its preferred cover, the female seems elusive 

 and nests are difficult to find. Sutton has remarked that they are 

 "rather deliberate, even vireo-like in their movements" (Van Tyne 

 and Sutton, 1937). In the Chisos Mountains, they frequented espe- 

 cially the young maples and deciduous oaks along the banks of the 

 dry, boulder-strewn stream bed, and elsewhere on the steep mountain 

 slopes their preference for clumps of small oaks was noted. 



Voice. — The call note of the Colima warbler is a very sharp, almost 

 explosive 'psit. Its common song is a continuous trill, like that of the 

 chipping sparrow, but shorter (lasting 3 to 4 seconds), more musical, 

 and ending with two separate notes slightly lower in scale. A second, 

 rarer, and more varied song is so clear that it can be heard for three 



