Part 2 (1/2)

On the basis of the evidence presently available, we are reluctant to follow Sutton (1950:136) in a.s.signing breeding birds from the Gulf coastal region to _C. s. inornatus_, a name otherwise applied to a population of birds breeding inland, in northwestern North America south to central Utah and Colorado and east to South Dakota (and formerly to western and southeastern Minnesota and Iowa; see A.O.U.

Check-list, 1957:190). The intermediate characters of birds breeding in coastal Texas and Tamaulipas probably represent not the results of actual genetic intermixing of the two named populations but, rather, an adaptive response of the eastern coastal stock (_C. s. semipalmatus_) to environmental modalities distinct from those operating elsewhere within the range of the eastern coastal population or on the inland population. Accordingly, we tentatively use the name _C. s.

semipalmatus_ for our Tamaulipan specimens, realizing that the patterns of geographic variation in the species do not lend themselves well to taxonomic treatment by the trinomial nomenclatural system. The need for a comprehensive a.n.a.lysis of geographic variation in this species, based, if possible, on proper segregation of age cla.s.ses along the lines followed by Pitelka (1950) for _Limnodromus_, is obviously indicated.

PLATE 5

[Ill.u.s.tration: Map of coastal Tamaulipas, showing the barrier island and localities mentioned in text. Stippled areas are extensively marshy.]

PLATE 6

[Ill.u.s.tration: FIG. 1.--_Croton_ and _Fimbristylis_ on stabilized dunes; the Laguna Madre and surrounding alkaline flats and clay dunes are visible in the background. Habitat of Road-runner, Ord kangaroo rat, and keeled lizard.]

[Ill.u.s.tration: FIG. 2.--Active dune near Camp 1. Other active dunes can be seen in the background, in the right foreground is a clump of _Croton_, and in the left foreground is a small clump of _Fimbristylis_. Habitat of Road-runner, Ord kangaroo rat, and keeled lizard.]

=_Arenaria interpres morinella_= (Linnaeus): Turnstone.--Approximately 40 individuals were noted along the beach from July 6 to 10, mostly in small groups; the largest flock included 15 individuals. Specimens (5): [M], 38931, testis 4 1 mm., moderately fat, 107 gm., 4 P old; [M], 38932, testis 3 1 mm., moderately fat, 103 gm., molting; 75 miles south of Was.h.i.+ngton Beach, July 8. Male, 38928, testis 2 mm., 111 gm., 3 P old; [M], 38929, testis 3 mm., moderately fat, 106 gm., 6 P old; [M], 38930, testis 2.5 mm., moderately fat, 108 gm., 6 P old; Camp 2, July 9.

The only previous record of the Turnstone in Tamaulipas is an observation of an unspecified number at Tepehuaje on May 9, 1949 (Robins, Martin, and Heed, 1951). The dates of our records suggest that nonbreeding birds summer along the coast of Tamaulipas. The species is present in small numbers in summer along the central Gulf coast of Texas (Hagar and Packard, 1952:8). Loetscher (1955:26-27) does not report records for Veracruz in summer, but records of the species in Yucatan on May 31, 1952 (Paynter, 1955:101), and on June 16, 1900 (Mexican Check-list, 1950:79), probably represent summering nonbreeders. Probably also in the same cla.s.s are supposed ”migrants”

seen at Coatzacoalcos on May 17, 1954, and June 4, 1955 (Coffey, 1960:290).

Inasmuch as Haverschmidt (1955:368) reports that nonbreeding birds summering in Surinam only occasionally a.s.sume breeding plumage, it is noteworthy that our specimens were molting from nuptial (summer) to winter plumage. None of the nonbreeding northern sh.o.r.ebirds observed by Eisenmann (1951:183) in Panama in summer were in nuptial plumage.

=_Crocethia alba_= (Pallas): Sanderling.--This sandpiper was noted each day along the beach, occasionally singly but more frequently in groups ranging from 10 to 50 individuals. Specimens (7): [M], 38936, testis 2 mm., light fat, 49 gm., 5 P old, Camp 1, July 7. Female, 38937, ova to 1 mm., fat, 58 gm., 4 P old; [M], 38939, fat, no weight recorded, 6 P old, breeding plumage; 3 [M] [M], 38940-38942, fat, no weight recorded, 4-5 P old; Camp 2, July 9.

With one exception as noted, our specimens are in worn, nonbreeding plumage and are replacing their old feathers with new ones fundamentally the same in color and pattern; the exceptional specimen is molting from worn breeding plumage into nonbreeding plumage. Only one other individual in breeding feather was seen on the island.

According to the Mexican Check-list (1950:99), the Sanderling has been recorded in Mexico from August to May 19. In Texas, Peterson (1960:107) reports that it is a migrant, April to June and July to November, and that it winters along the coast. We suspect that many of the birds present in Texas in June and July, together with those recorded by us in Tamaulipas in July, are nonbreeding, summering individuals.

Haverschmidt (1955:368) reports northern-summer records from Surinam, and, according to the A.O.U. Check-list (1957:208), nonbreeding birds occur in summer extensively through winter range of the species, including the Gulf coast of the United States.

=_Micropalama himantopus_= (Bonaparte): Stilt Sandpiper.--Two birds in worn winter plumage were taken as they foraged together at the edge of the laguna near Camp 2 on July 9. Specimens (2): [M], 38934, testis 2.5 mm., heavy fat, 116 gm., 4 P old; [M], 38935, testis 3 mm., fat, 111 gm., 4 P old.

Our specimens probably were nonbreeding birds summering between the breeding range in arctic America and the winter range in northern South America. The A.O.U. Check-list (1957:202) does not mention nonbreeding, summering records of this species. The 251 birds seen by Coffey (1960:292) at Cacalilao, Veracruz, on May 11, 1954, were probably migrants.

=_Recurvirostra americana_= Gmelin: American Avocet.--This species was seen only in three large flocks flying south along the beach, as follows: 56 birds 72 miles south of Was.h.i.+ngton Beach, July 8; 38 birds 73 miles south of Was.h.i.+ngton Beach, July 8; 29 birds 72 miles south of Was.h.i.+ngton Beach, July 10. All birds were in winter plumage.

All these birds were possibly autumnal migrants, but the dates are early; the species has not previously been recorded on migration in Mexico before August (Mexican Check-list, 1950:101). The species is known to breed in San Luis Potosi (Mexican Check-list, _loc. cit._) and along the lower coast of Texas (”rarely to Brownsville”; A.O.U.

Check-list, 1957:209); avocets thus may also breed in coastal Tamaulipas.

=_Larus argentatus_= Pontoppidan: Herring Gull.--A first-year bird was observed near Camp 2 on July 8, and two subadult individuals were seen on the beach between the Third and Fourth pa.s.ses on July 8.

=_Larus atricilla_= Linnaeus: Laughing Gull.--This gull was common all along the beach. Many individuals were in full breeding feather and many subadult birds were also present. Specimens (6): [M] subadult, 38944, testis 5 1 mm., 325 gm., molting; [F], 38945, ovary small, 309 gm., in molt, brood patches refeathering; s.e.x?, 38943, 315 gm., in molt; s.e.x? subadult, 38946, 327 gm., in molt; Camp 1, July 7. Female subadult (second-year), 38947, 305 gm., in molt, Camp 2, July 8.

Female, 38926, ova to 2.5 mm., 313 gm., 8 P old, Camp 2, July 10.

The Mexican Check-list (1950:105) refers to the Laughing Gull as a common winter resident on both coasts of Mexico from August 7 to May 17, but Loetscher (1955:29) found it locally common throughout the year on the coast of Veracruz, and he mentioned seeing birds a short distance south of Tampico in June and July. The status of this gull in Tamaulipas remains to be determined; probably it will be found breeding locally, but many of the birds summering in eastern Mexico are most likely nonbreeders (A.O.U. Check-list, 1957:226).

=_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 Was.h.i.+ngton 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): [M], 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 a.s.sociated 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).