The Thick-billed Parrot occurs in the southeastern section of the State, where it is fairly common. Moore (1947:27-28) described this parrot as Rhynchopsitta terrisi: he thought it differed decidedly from Rhynchopsitta pachyrhyncha. However, Hardy and Dickerman (1955:305-306) decided that uniting the two forms as a single species better expresses their relationship.
Burleigh and Lowery (1942:189) reported seeing a small flock of Thick-billed Parrots on the summit of Diamante Pass. Dickerman, in his field notes, wrote that at a place 13 mi. E San Antonio de las Alazanas, 9345 feet, a large flock of about 300 birds was in a spruce-fir-pine-aspen association.
*Coccyzus americanus americanus (Linnaeus).—Specimens examined: total 2: ♂ ♂ 32037-32038 from 12 mi. N, 12 mi. W Jiménez, 850 ft., June 19, 1952, measurements: wing, 141, 146 mm.; tail, 142, 149 mm.; tarsus, 27, 27 mm.; culmen, 25, 24 mm.
In Coahuila, the Yellow-billed Cuckoo seems to be uncommon. It occurs in the northeastern section of the State, in the Gulf Coastal Plain (Baker, 1956:128), and probably breeds there. One subspecies, americanus, has been recorded from Coahuila.
According to Ridgway (1916:13-17) the difference between C. a. americanus and C. a. occidentalis is size. His (loc. cit.) average measurements of males of occidentalis are: wing, 149.6 mm.; tail, 147.1 mm.; tarsus, 26.7 mm.; and culmen, 27.7 mm. whereas average measurements given by him of males of americanus are: wing, 143.6 mm.; tail, 140.7 mm.; tarsus, 25.2 mm.; and culmen, 26.4 mm. Van Tyne and Sutton (1937:35) question the value of maintaining the subspecies occidentalis, because individuals of americanus and occidentalis are almost impossible to tell apart. Friedmann, Griscom, and Moore (1950:132) stated that americanus occurs in eastern North America whereas occidentalis occurs in western North America. If the subspecies occidentalis exists, then Nos. 32037 and 32038 are, by size, americanus and No. 32038 is an intergrade between the two subspecies (or a large individual of americanus).
The Yellow-billed Cuckoo was seen also by Findley 2 mi. S and 3 mi. E San Juan de Sabinas on June 22, 1952, and by Dickerson at Torreón on July 2, 1955. The sizes of the testes of the birds from 12 mi. N and 12 mi. W Jiménez (9, 10 mm. long) and the date (June 19) on which they occurred there indicate that the birds possibly were breeding.
Coccyzus erythropthalmus (Wilson).—Miller (1955a:163) reported a migrant Black-billed Cuckoo taken in the maples and basswood near a water hole in the bottom of Boquillas Canyon in the Sierra del Carmen, 5200 feet, on April 22. Friedmann, Griscom, and Moore (1950:132) reported that this cuckoo is presumably a regular transient in México, but generally overlooked.
*Geococcyx californianus (Lesson).—Specimen examined: one, ♀ 32049, from 8 mi. N, 2 mi. W Piedras Negras, June 18, 1952.
Miller (1955a:163) heard several Roadrunners calling at Boquillas Canyon in the Sierra del Carmen, where he obtained two females. Burleigh and Lowery (1942:190) stated that the species proved to be "unexpectedly scarce" and was noted but once by them on April 22 when a single bird was observed in "the open desert west of Saltillo." Sutton and Burleigh (1939a:30) noted that the Roadrunner was not common anywhere in southern Coahuila; they obtained one female at San Pedro on January 29. The size of the largest ovum (15 mm. in diameter) of No. 32040 indicates that this species breeds in Coahuila.
*Crotophaga sulcirostris sulcirostris Swainson.—Specimen examined: one, ♀ 32039, from 2 mi. S, 3 mi. E San Juan de Sabinas, June 22, 1952.