Chlidonias niger surinamensis (Gmelin): Black Tern.—On July 6, 7, 8, 9, and on the morning of July 10, we saw this species only occasionally, recording in total not more than 50 individuals. But, about noon on July 10, we observed at least 300 birds in compact flocks of about 50 individuals each between Washington Beach and a point about 9 miles south of that locality. Approximately one in ten birds seen was in breeding plumage, the rest being in winter or subadult plumages, which are indistinguishable in the field. Perhaps some of the birds seen were nonbreeding, summering individuals, but we presume that the large groups were southbound migrants, and we note that autumnal migrants appear in northern Veracruz as early as July 1 (Loetscher, 1955:30). On the central Gulf coast of Texas, Hagar and Packard (1952:9) indicate that an influx of birds occurs in the last week of July, and small numbers of birds, presumably nonbreeding individuals, are present along the Gulf coast throughout June and July. Dresser (1866:45) found this species to be "common at the Boca Grande during the summer."
Specimens (2): ♂, 38948, testis 6 mm., moderately fat, 68 gm., in breeding plumage, Camp 1, July 7. Female, 38949, ovary inactive, 49 gm., molt into winter feather almost complete, Camp 2, July 10.
Hydroprogne caspia (Pallas): Caspian Tern.—The only published record of the Caspian Tern in Tamaulipas is a report of one seen at Lomas del Real on November 20, 1956 (Coffey, 1960:260), but we found it moderately common all along the beach and at the margin of the laguna. It was frequently associated with the Royal Tern, which outnumbered it better than three to one (see Table 2). The species is resident and breeds along the coast of Texas, and it probably has similar status in Tamaulipas. However, in Veracruz it is known only as a winter visitant (Loetscher, 1955:30) and as a spring migrant (Coffey, 1960:293). Specimen: ♀, 38950, ova to 2 mm., moderately fat, weight not recorded, 5 P old, Camp 2, July 9.
Sterna hirundo hirundo Linnaeus: Common Tern.—We took a specimen (♂?, 38951, no fat, 165 gm.), 49 miles south of Washington Beach on July 8, and saw two others over the laguna at Camp 2 on July 9. Our specimen had nearly finished with molt and feather growth into adult winter plumage. The status of Common Terns in Tamaulipas is uncertain; our record, and records from Tamós on July 1, 1952, and June 12, 1953 (Loetscher, 1955:29), probably pertain to nonbreeding, summering birds. Yet, the species has bred on the Texas Gulf coast (A.O.U. Check-list, 1957:235), and it reasonably may be expected to nest in Tamaulipas. Coffey (1960:293) saw two individuals at Altamira on May 10, 1954.
Sterna forsteri Nuttall: Forster Tern.—Six were recorded near Camp 1 on July 7, and two were seen on the beach on July 6 and 10. The Mexican Check-list (1950:108) does not cite records for Tamaulipas, but the A.O.U. Check-list (1957:234) includes northern Tamaulipas within the breeding range. Evidence suggesting breeding of the species in extreme northern Veracruz is reported by Loetscher (1955:29) in the form of a female specimen with "ovary greatly enlarged" taken seven miles west of Tampico on May 30, 1947. In the same area the species also seems to spend the summer as a nonbreeder, for Loetscher (loc. cit.) saw 20, nearly all in nonbreeding plumage, on July 1, 1952.
Specimens (4): ♂, 38952, testis 4.5 mm., 150 gm., 8 P old; ♂, 38955, testis 2 mm., 138 gm., 2 P old; ♂, 38953, testis 5 × 1 mm., 142 gm., 5 P old; ♀, 38954, ova to 1 mm., 148 gm., 2 P old; Camp 1, July 7.
Sterna albifrons antillarum (Lesson): Least Tern.—The status of this species in Tamaulipas is uncertain, but there is reason to believe that it breeds, at least in small numbers. We found the species moderately common and generally flying about in twos, possibly mated pairs, near both camps and on the beach. Breeding is suggested by the large sizes of the testes of the two males collected and by the presence of brood patches on a female taken on July 6, but we have no direct evidence of nesting in Tamaulipas, and it should be noted that this species is known to spend the summer in nonbreeding condition at many places (A.O.U. Check-list, 1957:239). Loetscher (1955:30) suggests that the species may be found breeding in Veracruz and mentions a record of 15 seen at Miramar, Tamaulipas, on June 26, 1952. Dresser (1866:45) found it to be "abundant" at the "Boca Grande" in summer.
On July 10, we saw flocks of 15 to 20 individuals flying along the beach a few miles south of Washington Beach.
Specimens (4): ♂, 38958, testis 11 × 4 mm. (right testis 5 × 4 mm.), light fat, 45 gm., 6 P old; ♂, 38959, testis 11 × 4 mm. (right testis 7 × 4 mm.), light fat, 45 gm., 6 P old; ♀, 38956, ova to 2.5 mm., 42.5 gm., 6 P old, brood patches refeathering; Camp 1, July 6. Female, 38957, ova to 1 mm., 44 gm., Camp 1, July 7. This last specimen had essentially completed the autumnal molt into winter plumage, with only a few feathers remaining ensheathed basally.
Our specimens are referable to S. a. antillarum, being paler dorsally and slightly lighter gray on the hind-neck than specimens of S. a. athalassos from Kansas, with which they were compared.