Thalasseus maximus maximus (Boddaert): Royal Tern.—This species was common all along the beach, occurring for the most part in flocks of from ten to 50 individuals in association with Cabot Terns. Data on gonadal condition and brood patches of some of our specimens suggest that breeding occurs in coastal Tamaulipas, as previously reported by the Mexican Check-list (1950:110). Robins, Martin, and Heed (1951) report seeing one Royal Tern near Tepehuaje on May 9, 1949, and Dresser (1866:44) found the species "common at the Boca del Rio Grande during the summer."
Specimens (6): ♂, 38960, testis 9 × 4.5 mm., not fat, 484 gm., 6 P old, brood patches refeathering, 4 miles south of Washington Beach, July 6. Male, 38961, testis 7 × 3 mm., 455 gm., no brood patches, 8 miles south of Washington Beach, July 6. Male, 38962, testis 10 × 5 mm., 387 gm., brood patches refeathering; ♀, 38963, ova to 1 mm., 358 gm., 3 P old; ♀, 38964, ova to 3 mm., 389 gm., 8 P old; Camp 1, July 7. Female, 38994, ova to 2 mm., 536 gm., brood patches refeathering, Camp 2, July 10.
Thalasseus sandvicensis acuflavidus (Cabot): Cabot Tern.—This tern was moderately common along the beach and margin of the laguna, and it was seen frequently in company with Royal Terns. Like the latter, this tern breeds in coastal Texas (A.O.U. Check-list, 1957:241), and it probably also nests in Tamaulipas, although direct evidence is not available. The only previous record of this species in Tamaulipas is a report (Robins, Martin, and Heed, 1951) of two observed on the beach near Tepehuaje on May 9, 1949.
Specimens (4): ♂, 38965, testis 9 × 4.5 mm., 208 gm., 9 P old, 49 miles south of Washington Beach, July 8. Male, 38966, testis 8 × 3 mm., not fat, 192 gm., 8 P old; ♀, 38967, ova to 3 mm., 193 gm., 7 P old, brood patches refeathering; ♀, 38968, ova to 1 mm., 186 gm., 8 P old, no brood patches; 52 miles south of Washington Beach, July 8.
Rynchops nigra nigra Linnaeus: Black Skimmer.—We found this species moderately common at the edge of the laguna at both camps and occasionally saw it along the beach. Generally two birds, probably mated pairs, were seen together; twice birds were seen carrying food in their bills, presumably intended for nestlings. The species is known to nest in Tamaulipas from "Matamoros Lagoon" south to Tampico (Mexican Check-list, 1950:112).
Specimens (2): ♂, 38970, testis 40 × 23 mm. (abnormally large, possibly as a result of hemorrhage), 418 gm., brood patches refeathering; ♂, 38969, testis 17 × 4 mm., fat light, 442 gm., brood patches refeathering; Camp 1, July 7.
Zenaidura macroura Linnaeus: Mourning Dove.—Our only record is a lone bird seen in a mesquite near Camp 1 on July 6. Possibly the species breeds along the margin of the laguna, although Aldrich and Duvall (1958:113, map) do not include coastal Tamaulipas in the known breeding range. Loetscher (1955:30) suggests that the Mourning Dove may be found breeding in the lowlands of northern Veracruz and cites a record of one seen at Tamós on July 1, 1952.
Geococcyx californianus (Lesson): Road-runner.—At least four individuals were seen in large dunes at Camp 1 on July 7 and 8. On several occasions we watched them pursue lizards (Holbrookia propinqua) at the margins of clumps of Croton and Ipomoea.
Chordeiles minor aserriensis Cherrie: Nighthawk.—Nighthawks of this species were seen regularly at Camp 1, where we flushed them from alkaline flats in the day and heard them calling as they foraged over the dunes in late afternoon.
Specimens (3): ♂, 38971, testis 5 mm., no fat, 62 gm., Camp 1, July 6. Male, 38972, testis 7.5 mm., no fat, 58 gm.; ♂, 38973, testis ?, no fat, 53 gm.; Camp 1, July 7. The gonads of these birds were not in full breeding condition, but it is highly probable that the birds were members of a population that had bred in the area.