Part 6

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 Mexico 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 Leon 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, Mexico, 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 x 4 mm., not fat, 27.5 gm.; , 38979, testis 11 x 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 x 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.

Specimens (2): , 38985, testis 11 x 7 mm., not fat, 43 gm.; , 38984, ova to 4.5 mm., vascular brood patch, 49.0 gm.; Camp 1, July 7.

PLATE 7

PLATE 8

=Cassidix mexicanus prosopidicola= Lowery: Great-tailed Grackle.--Small, postbreeding flocks composed of both adult and juvenal birds were seen moving along the edge of the laguna at Camp 1. In the morning the flocks flew south, and in the afternoon groups of similar size flew north, presumably to a roost at an undetermined distance north of our camp. Occasionally, a few birds stopped to rest or to forage on the dunes or in stands of mesquite. At Camp 2 on July 9, a postbreeding adult female and a well-grown, presumably independent juvenile were taken as they perched in a clump of mesquite in which we found three old nests of Cassidix; two of the nests were about four feet apart in one tree, and the third was in another tree 100 feet from the first.

Specimens (4): adult, 38988, testis 6 mm., no fat, 209 gm., 6 P old, Camp 1, July 7. Female, 38989, ova to 3 mm., fat, 115 gm., old brood patch, Camp 1, July 8. Female, 38990, ova to 1 mm., moderate fat, 107 gm., 7 P old, brood patch refeathering; juv., 38991, testis 3 x 1 mm., not fat, 172 gm., 6 P old; Camp 2, July 9.

TABLE 4.--MEASUREMENTS IN MILLIMETERS OF ADULT MALES OF CASSIDIX MEXICANUS

=============+=========+=========+=========+===========+============ | | | | | Weight in LOCALITY | No. | Wing | Tail | Tarsus | grams -------------+---------+---------+---------+-----------+------------ Austin, Texas|17-137| 184.3 | 203.8 | 46.38 | 225.6 June | |(173-200)|(178-232)|(41.8-50.0)| (204-253) | | | | | 202.2 July | | | | | (195-207) | | | | | San Patricio | 5 | 185.2 | 204.2 | 46.74 | 237.6 Co., Texas| |(182-188)|(190-219)|(45.1-50.2)| (228-245) | | | | | Barrier Is., | | | | | Tamps. | 1 | 178 | 185 | 47.1 | 209 | | | | | Victoria, | 4 | 192.2 | 224.2 | 47.77 | 254.3 Tamps. | |(186-200)|(215-232)|(46.0-49.1)| (239-276) | | | | | Tampico, | | | | | Tamps. | 1 | 197 | 214 | 48.3 | 260 | | | | | Catemaco, | | | | | Veracruz | 1 | 193 | 216 | 48.2 | 257 -------------+---------+---------+---------+-----------+------------

Specimens from the barrier island are clearly referable to C. m. prosopidicola, showing no approach to the larger and, in the female, darker C. m. mexicanus of Veracruz and San Luis Potosi. In Table 4, measurements of the adult male from the barrier island may be compared with those of specimens of C. m. prosopidicola from Texas and a specimen of C. m. mexicanus from Veracruz; it is apparent that our specimen is assignable to the former.

Evidence of intergradation between the two subspecies is shown in a series of birds collected near Ciudad Victoria, Tamaulipas, in May, 1961. The females in the series are highly variable in color individually, but are on the average paler than C. m. mexicanus from Veracruz; the males are distinctly larger than C. m. prosopidicola from Texas. At Miramar, near Tampico, Tamaulipas, a decided approach to C. m. mexicanus is also evident in the dark color of females and in the large size of both males (Table 4) and females.

=Agelaius phoeniceus megapotamus= Oberholser: Red-winged Blackbird.--This species was recorded only at Camp 1 on July 7, when we saw two males, one of which was flying south along the edge of the dunes in a flock of five Great-tailed Grackles. Specimen: , 38992, testis 10 x 7 mm., fat, 54 gm., Camp 1, July 7. The large size of the testes of this individual indicates breeding condition.

=Sturnella magna hoopesi= Stone: Eastern Meadowlark.--Meadowlarks were found in small numbers along the margins of the alkaline flats at both camps. Breeding was still in progress, for males were singing and a female shot on July 9 had only recently laid eggs. Specimens (2): , 38986, testis 13 x 8 mm., not fat, 102 gm.; , 38987, ova to 6 mm., 3 collapsed follicles, not fat, 88 gm.; Camp 2, July 9.

=Richmondena cardinalis canicaudus= Chapman: Cardinal.--This species was recorded only in stands of mesquite near Camp 1, as follows: July 7, two pairs seen, from which a breeding female was taken; July 8, three birds seen. Specimen: , 38933, edematous brood patch, 36.5 gm., Camp 1, July 7. Intergrades between the present subspecies and R. c. coccinea of Veracruz are reported from Altamira, Tamaulipas (Mexican Check-list, 1957:329).

Mammals

=Dasypus novemcinctus mexicanus= Peters: Nine-banded Armadillo.--Remains of an armadillo (89017) were found in a mesquite thicket in the dunes near Camp 1 on July 7. The bones are not badly weathered and were not embedded in sand.

This species has not been recorded previously on the barrier island of Tamaulipas, nor, for that matter, on any of the barrier islands on the western shore of the Gulf of Mexico.

=Lepus californicus merriami= Mearns: Black-tailed Jackrabbit.--From two to four individuals were recorded daily in dunes and on alkaline flats in the vicinity of stands of mesquite and cactus.

Specimens (2): adult, 89018, pregnant (two embryos, 28 mm. in crown-rump length), Camp 1, July 6. Male immature, 89019, Camp 1, July 7. Our specimens have been compared with two skins of L. c. curti from the type locality at Eighth Pass, with which they agree reasonably well in color. The size of the adult female is about that characteristic of other specimens of adult L. c. curti, but characters of the skull are consistent with those of L. c. merriami.

A specimen of this species from Matamoros and several from Brownsville, Texas, have been assigned by Hall (1951:43) to L. c. merriami. Specimens from Padre Island, Texas, reportedly resemble L. c. curti in smallness of the tympanic bullae but are in other characters referable to L. c. merriami (Hall, 1951:44).

=Spermophilus spilosoma annectens= (Merriam): Spotted Ground Squirrel.--These squirrels were moderately common in dunes at both camps. They were heard calling, and many tracks and holes were seen. On July 7, at Camp 1, a lactating, adult female (89020) and two dependent juveniles (89021, skull only, 89022, skin and skull) were shot at the entrance of a burrow; the uterus of the adult showed six placental scars.

Our adult specimen has been compared with ten specimens obtained by Hall and von Wedel at Eighth Pass in March, 1950; ours differs from the ten in being paler and slightly larger. The pallor is perhaps attributable to seasonal variation, and the size (246-79-38-7; weight, 133 gm.) is within limits that would be expected in a larger series of the population sampled by Hall and von Wedel. Hall (1951:38) referred specimens of this squirrel from Eighth Pass to S. s. annectens.