Variation in Chordeiles minor in Tamaulipas has recently been studied by Graber (1955). Two specimens taken by him on August 3, 1953, approximately 9 miles south of Carbonera, resemble birds from Terrell County, Texas, and represent C. m. aserriensis, as do our three birds from the barrier island. Two of Graber's specimens from Lomas del Real, in southeastern Tamaulipas, are distinctly darker and probably represent C. m. neotropicalis, a subspecies subsequently described from Chiapas (Selander and Alvarez del Toro, 1955).
Muscivora forficata (Gmelin): Scissor-tailed Flycatcher.—On July 7 near Camp 1, two individuals were found in stands of mesquite. One was taken and proved to be an adult male (38974, testis 6 × 3 mm., not fat, 40 gm.) in postnuptial molt (6 P old).
We presume that the two birds recorded by us were members of a population breeding on the barrier island, rather than autumnal migrants. The Mexican Check-list (1957:69) records this species in México only as a transient and winter visitant. But, on the basis of records of birds seen along the highway between Matamoros and Ciudad Victoria, Davis (1950) has suggested that the species breeds in Tamaulipas, and this is supported by a report of one seen at the north end of the Monterrey Airport on June 1, 1957 (Coffey, 1960:294). Brown (1958) has recently established that the species breeds in Nuevo León by finding a nest 33 kilometers (by road) north of Sabinas, Hidalgo, on July 19, 1954.
Myiarchus cinerascens cinerascens (Lawrence): Ash-throated Flycatcher.—A juvenal male (38975, testis 2 mm., no fat, 35.0 gm.) taken in mesquite at Camp 1 constitutes our only record for this species. Lanyon (1961:441, map) has shown that most of Tamaulipas is devoid of these flycatchers in the breeding season; the nearest known breeding Ash-throated Flycatchers are slightly west of Corpus Christi, Texas, about 200 miles north-northwest of Camp 1 on the barrier beach. Our specimen closely resembles eight specimens from Coahuila, México, in general coloration and, especially, in the pattern of colors on the outer rectrices. Probably No. 38975 was from southwestern Texas or Coahuila and had begun its southward migration. Against this idea lies chiefly the fact that young-of-the-year tend to move south later than adults of the same species; so, this bird possibly had been reared in coastal Tamaulipas.
Eremophila alpestris giraudi (Henshaw): Horned Lark.—This species occurred in moderate numbers on alkaline flats and almost barren sand flats at both camps. At the time of our visit to the island, the breeding season apparently was coming to an end, but we noted no tendency in the birds to flock.
Specimens (7): ♂, 38981, testis 6 mm., 21.0 gm.; ♂, 38977, testis 7.5 × 4 mm., not fat, 27.5 gm.; ♂, 38979, testis 11 × 7 mm., 29.0 gm.; ♀, 38976, ova to 3 mm., brood patch vascular but regressing, no fat, 24.4 gm.; sex? juv., 38987, no fat, 21.0 gm.; sex? juv., 38980, 24.0 gm.; Camp 1, July 7. Male, 38982, testis 9.5 × 6 mm., 27.5 gm., Camp 2, July 9.
The subspecies E. a. giraudi, which is endemic to the Gulf coastal plain of Texas and Tamaulipas, has been reported in Tamaulipas previously only from Bagdad, near Matamoros (Mexican Check-list, 1957:106). The fact that our specimens show characters totally consistent with those of E. a. giraudi indicates that there is little genetic interchange between the population we sampled and those of E. a. diaphora, the closest of which reportedly breeds at Miquihana, in southwestern Tamaulipas.
Corvus cryptoleucus Couch: White-necked Raven.—Several groups of six to ten birds were present at Washington Beach on July 6 and 10; but, southward on the island, we recorded this species only once, on July 9, when a lone individual flew near Camp 2, being pursued and "buzzed" by two Least Terns. The Mexican Crow (Corvus imparatus) reportedly is common in the coastal region of Tamaulipas (Mexican Check-list, 1957:118) but was not seen by us.
Thryomanes bewickii cryptus Oberholser: Bewick Wren.—This species seemingly breeds in small numbers in mesquite stands near Camp 1, where we obtained a juvenile and saw another individual. Specimen: ♀ juv., 38983, no fat, 10.0 gm., Camp 1, July 8. T. b. cryptus is reported to intergrade with T. b. murinus of Veracruz in southern Tamaulipas (Mexican Check-list, 1957:160-161).
Mimus polyglottos leucopterus (Vigors): Northern Mockingbird.—We recorded this species only near Camp 1, where a few pairs were breeding in stands of mesquite. Males were in full song and territorial display.