=_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): [M], 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; [F], 38963, ova to 1 mm., 358 gm., 3 P old; [F], 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): [M], 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; [F], 38967, ova to 3 mm., 193 gm., 7 P old, brood patches refeathering; [F], 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): [M], 38970, testis 40 × 23 mm. (abnormally large, possibly as a result of hemorrhage), 418 gm., brood patches refeathering; [M], 38969, testis 17 × 4 mm., fat light, 442 gm., brood patches refeathering; Camp 1, July 7.