Hartlaub's Warbler is uncommon in Coahuila and seems to occur only in the southeastern section of the State; No. 31591 is the first record of the species in Coahuila. The size of the testes (5×2 mm.) of No. 31591 and the fact that the bird was singing when first seen suggest the possibility that V. s. mexicana breeds in southeastern Coahuila. Breeding there is not unexpected because the species has been found breeding in Nuevo León (Miller, Friedmann, Griscom, and Moore, 1957:242).
Parula americana (Linnaeus).—Miller (1955a:172) obtained a migrant Parula Warbler in an oak grove at 7000 feet on April 16 in the Sierra del Carmen, and remarked that it was "apparently the first record of this species in Coahuila."
*Parula pitiayumi nigrilora Coues.—The AOU Check-list Committee (1957:486) recorded this subspecies of the Olive-backed Warbler as a resident at Sabinas.
*Peucedramus taeniatus arizonae Miller and Griscom.—This subspecies of the Olive Warbler is locally common in Coahuila. Miller (1955a:172) found P. t. arizonae common in the pine timber above 6800 feet in the Sierra del Carmen and suggested that this warbler breeds in these mountains. Burleigh and Lowery (1942:203) found the Olive Warbler in a thick pine wood at an elevation of 9500 to 10,000 feet and remarked that this species was "decidedly uncommon in the Diamante Pass area." They (loc. cit.) obtained a female (not identified to subspecies) on April 23 that had a "well developed brood patch and was unquestionably incubating eggs." Sutton and Burleigh (1939a:40) took a single female at Diamante Pass on March 6 which also was not identified to subspecies. Dickerman saw Olive Warblers in the Sierra de la Madera on December 13, 1953, and 13 mi. E San Antonio de las Alazanas on April 10, 1954.
Dendroica petechia morcomi Coale.—Miller, Friedmann, Griscom, and Moore (1957:246) reported this subspecies of the Yellow Warbler as having been recorded from Coahuila.
Dendroica auduboni auduboni (Townsend).—Specimens examined: total 2: ♂ 31094 (skeleton only) from Fortín (=33 mi. N, 1 mi. E San Gerónimo), 3300 ft., March 29, 1952; and ♂ 31093 from 4 mi. W Hacienda La Mariposa, 2300 ft., March 25, 1952, weight, 12.3 gms.
Audubon's Warbler is a common winter visitant and migrant in Coahuila. Miller (1955a:173) recorded D. a. auduboni as a migrant from April 7 to 26 in the Sierra del Carmen; he found no suggestion of breeding by the Audubon's Warbler in the northwestern section of the State. One individual that Miller (loc. cit.) obtained was extensively black and approached the characters of the subspecies nigrifrons of Chihuahua. He (loc. cit.) suggested that the black individual was taken from "part of a cline of blackness and size in which D. a. auduboni of the northwest and D. a. nigrifrons of Mexico are extremes." Burleigh and Lowery (1942:203) remarked that Audubon's Warbler "is doubtless a common winter bird in the area around Saltillo." Two specimens obtained by Burleigh and Lowery (loc. cit.) "might be considered intermediate" between auduboni and memorabilis. Sutton and Burleigh (1939a:40) saw Audubon's Warbler "in some numbers near San Pedro ... [on] January 29 and 30." Dickerman saw Audubon's Warblers 13 mi. E San Antonio de las Alazanas on April 10, 1954. Miller (1955a:173) also obtained, in the Sierra del Carmen, a hybrid between D. coronata and D. auduboni.
Dendroica auduboni memorabilis Oberholser.—Oberholser (1921:246) recorded D. a. memorabilis from Saltillo on April 17. This subspecies seems to winter commonly in western México and less commonly in the Central Plateau and Sierra Madre Oriental (Miller, Friedmann, Griscom, and Moore, 1957:249-250).
Dendroica nigrescens (Townsend).—Specimen examined: one, ♂ 31095, from Fortín (=33 mi. N, 8 mi. W San Gerónimo), 3300 ft., March 28, 1952, weight, 9.3 gms.
The Black-throated Gray Warbler is an uncommon spring and possibly fall migrant in Coahuila. Miller (1955a:173) found D. nigrescens uncommon in the Sierra del Carmen. He saw and heard a spring migrant singing on April 12 at 7000 feet and obtained a male on April 16.