Chapter I: Part 1

UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 12, No. 7, pp. 309-345, pls. 5-8.

June 18, 1962

Vertebrates from the Barrier Island of Tamaulipas, Mexico

BY ROBERT K. SELANDER, RICHARD F. JOHNSTON, B. J. WILKS, AND GERALD G. RAUN

UNIVERSITY OF KANSAS LAWRENCE 1962

UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 12, No. 7, pp. 309-345, pls. 5-8.

June 18, 1962

Vertebrates from the Barrier Island of Tamaulipas, Mexico

BY

ROBERT K. SELANDER, RICHARD F. JOHNSTON, B. J. WILKS, AND GERALD G. RAUN

UNIVERSITY OF KANSAS LAWRENCE 1962

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Theodore H. Eaton, Jr.

Volume 12, No. 7, pp. 309-345 Published June 18, 1962

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY JEAN M. NEIBARGER, STATE PRINTER TOPEKA, KANSAS 1962

29-3002

Vertebrates from the Barrier Island of Tamaulipas, Mexico

BY

ROBERT K. SELANDER, RICHARD F. JOHNSTON, B. J. WILKS, and GERALD G. RAUN

Lying between the Gulf of Mexico and the Laguna Madre de Tamaulipas is a narrow barrier island extending from the delta of the Rio Grande south for 140 miles to within 185 miles of Tampico, Tamaulipas (Plate 5). This island, like most of coastal Tamaulipas, has been all but neglected by zoological collectors. Consequently, little is known of the kinds, distribution, and seasonal status of the vertebrates occurring there. The present paper is a report on land vertebrates collected and observed on the northern part of the barrier island of Tamaulipas from July 6 to 10, 1961. Our collection, which has been deposited in the Museum of Natural History, The University of Kansas, consists of 63 reptiles, 33 mammals, and 97 birds (58 skins, 19 skeletons, and 20 alcoholics).

Acknowledgments

We are especially indebted to Dr. Charles H. Simpson of Sinton, Texas, who generously placed at our disposal his truck, a four-wheel drive "Land Rover," without which travel on the island would have been difficult. We also acknowledge a loan of field equipment provided by Dr. Clarence Cottam, Director of the Welder Wildlife Research Foundation, Sinton, Texas.

Financial support for the present research was provided by grants from the National Science Foundation to The University of Texas (G 15882) and to The University of Kansas (G 10043).

Permits to collect vertebrates in Mexico were supplied by Ing. Luis Macias Arellano, El Director General, Departamento de Conservacion de la Fauna Silves, Mexico, D. F.

We are indebted to Dr. Richard H. Manville for arranging a loan of specimens of _Geomys personatus tropicalis_ in the United States National Museum. Dr. Marshall Johnston kindly identified specimens of plants from the barrier island. Several bones of birds and mammals were identified by Dr. Pierce Brodkorb and Dr. E. L. Lundelius. Mr. J. Knox Jones identified some of the mammalian material, and Dr. W. E. Duellman verified the identifications of the lizards; we thank all of these men for their willing assistance.

The Ecological Setting

The barrier island of Tamaulipas geologically and ecologically resembles Padre Island, of the Gulf coast of lower Texas, north of the mouth and delta of the Rio Grande. South of the delta, the island in Tamaulipas is a narrow strip of sand less than a mile in average width and is broken by a series of narrow inlets or "passes" through which water from the Gulf of Mexico mingles with that of the Laguna Madre de Tamaulipas. The passes are subject to recurrent opening and closing. North of the mouth of the Rio Soto la Marina, eight passes are designated by local fishermen, but only three, the Third, Fourth, and Fifth, were open at the time of our visit.

The Laguna Madre de Tamaulipas is described by Hildebrand (1958) in connection with a preliminary study of the fishes and invertebrates there. The average depth is probably less than 70 cm. and the waters are hypersaline. In the time of the recent drought in Texas and northeastern Mexico, salinity varied from 108 to 117 parts per thousand in the northern part of the laguna near Arroyo del Tigre (measurements taken in March, 1955) to from 39 to 48 parts per thousand in the southern part near Punta Piedras (measurements taken in October and November, 1953, and in March, 1954). Discussions of the geologic history, ecology, and zoogeography of the lagoons of the Gulf coast of the United States are given by Hedgpeth (1947; 1953).

Localities in coastal Tamaulipas mentioned in the text of this paper are shown on Plate 5.

The principal animal habitats are found in three vegetational associations (plates 6 and 7). On flats and low dunes lying between, and partly sheltered by, larger active dunes, small clumps of _Croton punctatus_ and a sedge (_Fimbristylis castanea_) are the only conspicuous plants. Near the western edge of the dunes, _Ipomoea pescaprae_ var. _emarginata_ is mixed with _Croton_, and there are scattered clumps of shrubby wolf-berry (_Lycium carolinianum_ var. _quadrifidum_), and mesquite (_Prosopis juliflora_).

The dunes are relatively stabilized on the western side of the island, and there we found moderately dense stands of mesquite trees reaching heights of from eight to 10 feet. Prickly-pear cactus (_Opuntia lindheimeri_) was common in those stands of mesquite, and we saw an occasional yucca tree. A fairly dense ground cover was formed by blanket-flower (_Gaillardia pulchella_), marsh-elder (_Iva_ sp.), _Flaveria oppositifolia_, _Enstoma exaltatum_, and _Croton capitatus_ var. _albinoides_.

A more open, xeric expression of the mesquite-cactus vegetation occurs on exposed, low clay dunes (see description by Price, 1933) located on alkaline flats bordering the laguna. At the time of our visit, most of the mesquites in these stands were dead or dying, the cactus was abundant, and the ground cover, which was sparse, included drop-seed (_Sporobolus virginicus_), ragweed (_Ambrosia psilostachya_), and _Commicarpus scandens_.

On alkaline flats flooded by hypersaline waters of the laguna following heavy rains, _Batis maritima_ is found in the lower areas, but on the slightly elevated areas there is low and almost continuous cover of _Monanthochloe littoralis_, in which can be found _Batis_, _Borrichia fructescens_, _Salicornia_ sp., _Iva_ sp., and sea-lavender (_Limonium carolinianum_).

Near Third Pass, sea oats (_Uniola paniculata_), evening primrose (_Oenothera_ sp.), and cordgrass (_Spartina_ sp.) are present on the dunes, and on alkaline flats we collected _Conocarpus erectus_, _Leucaena_ sp., and _Cassia fasciculata_ var. _ferrisiae_.

Itinerary

We reached Washington Beach from Matamoros on July 6, and drove to a point approximately 33 miles south on the beach, where we made Camp 1 on the east side of large dunes 400 yards from the surf. From this camp we worked the beach and dunes and also visited alkaline flats adjacent to the Laguna Madre. On the afternoon of July 8, we drove south along the beach and established Camp 2 on the south side of the Third Pass, approximately 73 miles south of Washington Beach. We had intended to go farther south but were unable to cross the Fourth Pass, an inlet three miles south of the Third Pass. We left the barrier island on the afternoon of July 10, after driving north from Camp 2 to the mouth of the Rio Grande, 11 miles north of Washington Beach.

Mexican fishermen camped at the Fourth Pass told us that, had we been able to cross the Fourth Pass, it would have been possible to drive south on the beach all the way to La Pesca, a fishing village near the mouth of the Rio Soto la Marina, approximately 150 miles south of Washington Beach.

Summary of Previous Work in the Area

The ornithologist H. E. Dresser (1865-1866) worked in southern Texas and at Matamoros, Tamaulipas, in 1863, and on one occasion reached the mouth of the Rio Grande ("Boca Grande"). He did not visit the barrier island or the Laguna Madre de Tamaulipas.

In their extensive travels through Mexico, E. W. Nelson and E. A. Goldman made collections at three localities in the coastal region of Tamaulipas but did not reach the barrier island (Goldman, 1951). Goldman collected at Altamira, near Tampico, from April 2 to 24, 1898, and from May 15 to 20 of the same year both he and Nelson made headquarters at Altamira. Nelson and Goldman also collected in the vicinity of Soto la Marina, 25 miles from the coast, from March 1 to 10, 1902, and, from February 13 to 15, they visited Bagdad, described by Goldman (1951:260) as "a village at very low elevation on the Rio Grande about 6 miles above the mouth of the river."

In March, 1950, C. von Wedel and E. R. Hall collected four species of mammals and one bird on the barrier island at Boca Jesus Maria (Eighth Pass). A report of this work published by Hall (1951) contains descriptions of three new subspecies of mammals from the island.

A few records of birds from the southern end of the barrier island and from other parts of coastal Tamaulipas were reported by Robins, Martin, and Heed (1951). In 1953, R. R. Graber and J. W. Graber made ornithological studies in the vicinity of Tampico and also reached the western edge of the Laguna Madre de Tamaulipas. Several papers on this work have appeared (Graber and Graber, 1954_a_, 1954_b_; Graber, 1955), but a comprehensive account of their observations and specimens was not published. Finally, J. R. Alcorn collected some sandpipers 20 miles southeast of Matamoros, on August 21, 1954, obtaining the first record of the Semipalmated Sandpiper (_Ereunetes pusillus_) in Tamaulipas (Thompson, 1958).

Accounts of Species

Catalogue numbers in the following accounts are those of the Museum of Natural History, The University of Kansas.

_Reptiles_

=_Gopherus berlandieri_= Agassiz: Texas Tortoise.--A pelvic girdle and complete shell with a few attached scutes (63494) were found in stabilized dunes at Camp 1 on July 7, and tracks were seen in the same area. Fragments of two other shells (63493, 63495) were found on sand flats between active dunes at Camp 1.

=_Holbrookia propinqua propinqua_= Baird and Girard: Keeled Earless Lizard.--This lizard was abundant on dunes and in pebble-strewn blow-out areas between dunes at Camp 2, but it occurred in smaller numbers in the less stabilized dunes of sparser vegetation at Camp 1. Breeding was in progress at both localities, as evidenced by the presence of eggs in the oviducts of several females, by the heightened coloration of both sexes, and by mating behavior.

The mating behavior of this species has not been described in the literature, and the following observations, made by Raun at Camp 2 on July 8, may be of interest. A male was seen to circle a female as the latter remained motionless with tail curved upward and to the side, exposing a patch of bright pink-orange color on the ventral surface of the tail. At times the male approached the female from the rear and slightly to the side, biting the dorsal part of her neck and simultaneously attempting to effect intromission. The female several times reacted to this approach by running forward a few steps, thereby freeing her neck from the grasp of the male. When the male did not attempt to approach again, the female appeared to invite copulation by moving in front of him with tail elevated and the colored ventral surface prominently displayed. At the time of copulation, the male mounted from the rear on the right side of the female, grasped her neck, and circled his tail beneath her tail; at the same time the hindquarters of the female were arched upward.

To confirm the presumed sexes of the two individuals under observation, both were collected while in copulation. Examination of the still-coupled specimens showed that both hemipenes of the male were everted and the left one had been inserted.

Apparently the pink-orange subcaudal patch of females is present only in the mating season. It was not present on specimens of this species taken by Raun and Wilks on Padre Island, Texas, in autumn, and it is not mentioned in taxonomic descriptions by Axtell (1954) and Smith (1946).

Measurements of adult specimens in our series indicate that females are of smaller average size than males, and, as previously noted by Smith (1946:132), females of this species have disproportionately shorter tails than do males (Table 1).

_Holbrookia propinqua_ was previously collected on the barrier island by Axtell (1954:31; see also Axtell and Wasserman, 1953:2), who took specimens at Boca Jesus Maria, at a locality six to seven miles south of Boca Jesus Maria, and at a point 20 miles east-southeast of Matamoros. Axtell (_loc. cit._) also lists specimens in the Museum of Zoology, University of Michigan, from Tepehuaje and from one mile north of Miramar Beach (Tampico).

Specimens (56): 3 [M] [M] adult, 1 [M] subadult, 63433-436, Camp 1, July 7. 33 [M] [M] adult, 63437-440, 63443-445, 63447, 63448, 63450-456, 63458, 63460, 63462, 63463, 63465-468, 63470-478; 13 [F] [F] adult, 63441, 63446, 63449, 63457, 63459, 63469, 63479-485; 6 juv., 63442, 63461, 63464, 63486-488; Camp 2, July 9-July 10.

TABLE 1.--MEASUREMENTS IN MILLIMETERS OF ADULT SPECIMENS OF _Holbrookia propinqua_ FROM THE BARRIER ISLAND OF TAMAULIPAS

=======+===========+=============+==========+=============== | Number | | | Ratio: SEX | of | Snout-vent | Tail | snout-vent | specimens | length | length | to tail -------+-----------+-------------+----------+--------------- Male | 33 | 56.0+-0.5[A] | 77.0+-0.7 | 0.731+-0.001 | | (49-62) | (69-85) | (0.682-0.817) -------+-----------+-------------+----------+--------------- Female | 14 | 50.9+-0.5 | 62.2+-0.9 | 0.825+-0.001 | | (47-53) | (57-68) | (0.735-0.877) -------+-----------+-------------+----------+---------------

[Footnote A: Mean +- standard error; range indicated in parentheses.]

=_Cnemidophorus gularis_= Baird and Girard: Whip-tailed Lizard.--At both camps we found this species in the same general habitat in which _Holbrookia_ occurred, but in numbers decidedly fewer than the latter.

Specimens (4): 2 [F] [F] adult, 63489, 63490, Camp 1, July 7. 1 [M] adult, 63491, 1 [F] adult, 63492, Camp 2, July 9.

We failed to take specimens of snakes on the barrier island, but tracks of snakes were noted on two occasions in dunes near Camp 1; one trail led into a burrow of a kangaroo rat.

_Birds_

Unless otherwise indicated, specimens taken were not molting. For birds undergoing postnuptial or postjuvenal molt, the degree of advancement of the molt is indicated by recording the number of primaries of the old plumage that have not been dropped. For example, the designation "4 P old" signifies that all primaries except the distal four have been molted.

Table 2 presents results of a strip census of birds along the strand, made by three of us from the moving truck on the morning of July 10. Birds characteristically found on sand near the surf were thus conveniently counted in accurate fashion. Birds not ordinarily found on the strand could not be treated this way; most were considerably less abundant than the eight most numerous species listed in Table 2. Over-all, the numbers of individuals listed are a good index of abundance of the Great Blue Heron and of the common charadriiform birds on the beach in early July. The Black Tern is an exception, however, and this is discussed in the account of that species on page 327.

TABLE 2.--BIRDS[A] RECORDED ALONG 17 MILES OF BEACH[B] ON THE BARRIER ISLAND OF TAMAULIPAS

=====================+=============+================ Species | Number | Birds per mile ---------------------+-------------+---------------- Great Blue Heron | 9 | 0.5 Oyster-catcher | 1 | 0.1 Black-bellied Plover | 20 | 1.2 Wilson Plover | 53 | 3.1 Willet | 43 | 2.5 Sanderling | 55 | 3.2 Laughing Gull | 136 | 8.0 Black Tern | 19 | 1.1 Caspian Tern | 82 | 4.8 Least Tern | 221 | 13.0 Royal Tern | 301 | 17.7 Cabot Tern | 122 | 7.2 +-------------+---------------- | Total: 1062 | Total: 62.4 ---------------------+-------------+----------------

[Footnote A: Common Tern, Forster Tern, and Long-billed Curlew also seen but not counted.]

[Footnote B: Between 56 and 73 miles south of Washington Beach, 11:00 to 11:45 a. m., July 10, 1961.]

=_Pelecanus erythrorhynchus_= Gmelin: American White Pelican.--A flock of approximately 300 individuals was seen resting at the edge of the Laguna Madre near Camp 2 on July 9. When disturbed by gunshots, the birds circled high over the laguna and flew to the west. Among bones found on sand flats at Camp 1 are a left tarsometatarsus and a pedal phalanx of an American White Pelican.

Supposedly the only breeding colony of this species on the northern Gulf coast is one in the Laguna Madre near Corpus Christi (Peterson, 1960:8), but the possibility of one or more such colonies existing in northeastern Tamaulipas has been suggested by Amadon and Eckelberry (1955:68) on the basis of their observations of individuals seen soaring near the coast 15 to 20 miles south of Brownsville on April 15 and June 5, 1952. According to Hildebrand (1958:153, and personal communication, August 14, 1961), small colonies of white pelicans do breed in some years on two small islands, in the Laguna Madre of Tamaulipas, located at 25 deg. 26' North and 93 deg. 30' West.

In Veracruz the species is recorded as a winter visitant and transient (Loetscher, 1952:22; Amadon and Eckelberry, 1955:68). Coffey (1960:289) reports the following observations for Veracruz and Tamaulipas: a flock of 52 between Tlacotalpan and Alvarado, May 29, 1951; 80 near Cacaliloa, April 20, 1958; 180 birds north of Alvarado, April 24, 1958; four at Altamira, May 28, 1955; flocks of three, 13, and 37 "south" of Matamoros, May 20, 1951; 72 at Lomas del Real, November 20, 1956.

=_Pelecanus occidentalis_= Gmelin: Brown Pelican.--Three individuals flew north over the surf near Camp 1 on July 7, and a lone bird was seen diving into the Gulf a short distance beyond the surf near Camp 2 on July 9. Birds seen by us probably were of the population named _P. o. carolinensis_, which is resident along the Gulf coast (Mexican Check-list, 1950:21).

=_Phalacrocorax_= sp.: Cormorant.--From 80 to 100 adult and juvenal cormorants were on the laguna at Camp 2 on July 8 and 9. Probably they were Common Cormorants (_P. olivaceus_), but, because specimens were not taken, we cannot eliminate the possibility that some (or all) were Double-crested Cormorants (_P. auritus_). The former breeds in coastal lowlands of eastern Mexico, whereas the latter is known in eastern Mexico only as a winter visitant and has not been recorded in Tamaulipas (Mexican Check-list, 1950:24).

=_Fregata magnificens_= Mathews: Magnificent Man-o'-war Bird.--An observation of a lone bird circling high over the laguna at Camp 2 on July 9 seemingly constitutes the third record of this species in Tamaulipas. Previous records were reported by Robins, Martin, and Heed (1951:336), who found "large numbers" in the Barra Trinidad region (8 miles north of Moron) on April 27 to 29, 1949, and mentioned an immature male taken at Tampico on April 23, 1923; this specimen has been identified by P. Brodkorb as _F. m. rothschildi_.

=_Ardea herodias_= Linnaeus: Great Blue Heron.--Our records of this heron are limited to the following observations: four individuals on the beach and seven in the laguna at Camp 1, July 7; one on the beach 52 miles south of Washington Beach, July 8; one 74 miles south of Washington Beach, July 8; two at Third Pass, July 8; 41 standing on mud-flats at the edge of the laguna near Camp 2, July 9; nine on the beach 56 to 73 miles south of Washington Beach, July 10; one on the beach 42 miles south of Washington Beach, July 10.

The status of the Great Blue Heron in coastal Tamaulipas remains to be determined. The subspecies _A. h. wardi_ (considered a synonym of _A. h. occidentalis_ by Hellmayr and Conover, 1948) is resident and breeds on the Gulf coast of Texas and is to be expected as a resident in Tamaulipas (Mexican Check-list, 1950:27). The species may breed south to Veracruz, where Loetscher (1955:22) reports it is "regular at nearly all seasons, chiefly on the coastal plain"; he records an observation near Tamos on July 1. The subspecies _A. h. herodias_ and _A. h. treganzai_ winter through much of Mexico and have been recorded in Tamaulipas (Mexican Check-list, 1950:27).

=_Florida caerulea_= (Linnaeus): Little Blue Heron.--We saw a white (immature) individual feeding with Reddish Egrets along an inlet at Camp 2 on July 8.

=_Dichromanassa rufescens rufescens_= (Gmelin): Reddish Egret.--This egret was recorded only about the inlet at Camp 2, where 15 individuals were feeding, either singly or in small groups, on July 8 and 9. We noted frequent use of the "Open Wing" method of foraging, as described by Meyerriecks (1960:108).

Specimen: [F] juv., 38899, ovary inactive, 587 gm., Camp 2, July 8. This specimen is referable to the nominate subspecies, which is resident along the Gulf coast. Our record seems to be the first for the species in Tamaulipas.

=_Leucophoyx thula_= (Molina): Snowy Egret.--Ten individuals of this species were feeding in association with Reddish Egrets in the inlet at Camp 2 on July 9.

=_Hydranassa tricolor_= (P. L. S. Mueller): Tricolored Heron.--An observation of one individual flying along the margin of the laguna near Camp 2 is our only record of this species.

=_Nycticorax nycticorax_= (Linnaeus): Black-crowned Night Heron.--This heron was found only at the edge of the laguna near Camp 2; ten individuals were noted on July 8, and 20 were seen perched in a clump of mesquite trees on July 9. Perhaps half the birds seen were in juvenal plumage. A juvenile was shot and examined on July 9 but was not preserved as a specimen.

There appears to be no definite evidence of breeding by this species in Tamaulipas (Mexican Check-list, 1950:32), but such may be expected because the species breeds locally in Texas (Peterson, 1960:19) and in Veracruz.

=_Ajaia ajaja_= (Linnaeus): Roseate Spoonbill.--On July 9 at Camp 2, 38 spoonbills flew up from the edge of the laguna where they had been resting near a large flock of white pelicans.

=_Cathartes aura_= (Linnaeus): Turkey Vulture.--One Turkey Vulture was seen flying east at a point 2 miles west of Washington Beach on July 10. It is noteworthy that we saw no Yellow-headed Vultures (_C. burrovianus_), a species recently recorded in the region of Tampico north to Lomas del Real (Graber and Graber, 1954_a_).

=_Colinus virginianus texanus_= (Lawrence): Bob-white.--This species was seen only in or near clumps of mesquite near Camp 1, where three covies (7, 13, and 18 individuals) were flushed on July 7. Specimen: [M] juv., 38900, testis 3 mm., 100 gm., 6 P old, Camp 1, July 7.

=_Porzana carolina_= (Linnaeus): Sora Rail.--On sand flats at Camp 1 we found a left humerus and several other post-cranial skeletal elements that have been identified by Dr. Pierce Brodkorb as belonging to this species. All the bones are of Recent age. We have no other record of the Sora Rail on the barrier island, but in all probability it occurs as a migrant and winter visitant along margins of the laguna.

=_Haematopus ostralegus_= Linnaeus: Oyster-catcher.--One individual was seen at Camp 2 on July 8, three were noted at the same locality on July 9, and one was present on the beach 72 miles south of Washington Beach on July 10. The only previous records of this species in Tamaulipas are a specimen ([M], 29348) taken by E. R. Hall 10 miles west and 88 miles south of Matamoros on March 20, 1950 (herewith reported for the first time), and three seen on the beach near Tepehuaje on May 9, 1949 (Robins, Martin, and Heed, 1951).

=_Squatarola squatarola_= (Linnaeus): Black-bellied Plover.--Plovers of this species were uncommon but regular on the beach; frequently two individuals were seen together, sometimes in association with one or more Willets. Specimens (4): [M], 38915, testis 4 mm., 231 gm.; [M], 38914, testis 4 mm., 221 gm.; [M], 38916, testis 3 mm., 209 gm., Camp 1, July 7. Male, 38917, testis 4 mm., 186 gm., Camp 2, July 9. The specimens were molting (3-4 P old) into winter plumage and showed little or no subcutaneous fat.

Our specimens and records probably pertain to nonbreeding individuals summering on the coast, as the species is known to do in Texas (Hagar and Packard, 1952:9) and elsewhere in its range (Eisenmann, 1951:182; Haverschmidt, 1955:336; A.O.U. Check-list, 1957:174). In any event, our dates (July 6 to 10) are unusually early for autumnal migrants; they do not reach Texas until August (Peterson, 1960:94), and Loetscher (1955:26) gives August 7 as the earliest date for southbound migrants in Veracruz.

=_Charadrius hiaticula semipalmatus_= Bonaparte: Ringed Plover.--We have a single record, an adult male (38913, testis 2 x 1 mm., heavy fat, 47.0 gm., 4 P old) taken on a sandbar at Camp 2 on July 9. The bird was feeding in company with a flock of Sanderlings.

There is no previous record of the Ringed Plover in Tamaulipas. In Texas, Hagar and Packard (1952:8) indicate that the first autumnal migrants reach the central Gulf coast in the last week of July. In coastal Mexico, the species has previously been recorded from August 23 to May 12 (Mexican Check-list, 1950:91). Therefore, the present record must represent an exceptionally early southbound migrant, or, more probably, a nonbreeding, summering individual. According to the A.O.U. Check-list (1957:166), nonbreeding birds are found in summer in coastal areas south to California, Panama, and Florida. Many individuals spend the northern summer along the coast of Surinam (Haverschmidt, 1955:336).

=_Charadrius wilsonia wilsonia_= Ord: Wilson Plover.--This small plover breeds commonly on the beach and on alkaline flats adjacent to the laguna. Previous evidence of breeding in Tamaulipas consisted only of a report of a male with brood patches and an enlarged testis taken near Tamos on May 30, 1947 (Loetscher, 1955:26).

We saw many pairs of adults and a large number of well-grown juveniles, and, at a point 4 miles south of Washington Beach, we collected a brood of three small juveniles that had only recently hatched. The breeding season apparently was drawing to a close, for several adults in our collection were in postnuptial molt and showed marked gonadal regression. From July 6 to 9, a few small groups of birds were noted, but large groups were not seen until July 10, when several flocks of up to 60 individuals were found along the coast 3 to 7 miles south of Washington Beach.

Specimens (12): [M], 38904, testis 4.5 x 2 mm., 58 gm., 3 P old, brood patches refeathering; [M], 38905, testis 5 x 2 mm., 59 gm., 4 P old, brood patches refeathering; [M] juv., 38903, 6.2 gm.; 2 sex?, 38901, 38902, 5.7 and 6.2 gm., 4 miles south of Washington Beach, July 6. Male, 38907, testis 5 x 2 mm., 56 gm., 7 P old, brood patches refeathering; [F], 38906, ova to 1 mm., 61 gm., 3 P old, brood patches refeathering; [F] juv., 38908, ovary inactive, 54 gm., in body molt; Camp 1, July 6. Male, 38910, testis 6 x 3 mm., 60 gm., 4 P old; [F], 38909, ova to 1 mm., 57 gm., 4 P old, brood patches refeathering; Camp 1, July 8. Male, 38911, testis 2 x 1 mm., 55 gm.; juv., 38912, no weight or sex recorded; Camp 2, July 9.

=_Numenius americanus parvus_= Bishop: Long-billed Curlew.--Lone individuals and groups of two to five were noted occasionally along the beach each day. In total, some 30 to 50 birds were counted, but some individuals may have been recorded more than once on different days. Specimens (2): [M], 38918, testis 4 mm., some fat, 459 gm., Camp 2, July 9; [F], 38933, ova to 1 mm., no weight recorded, Camp 2, July 8.

Our assumption that some or all individuals seen by us were nonbreeding, summering birds is supported by the fact that our specimens are referable to the small, northwestern subspecies, _N. a. parvus_, rather than to _N. a. americanus_; the latter breeds south in the eastern United States to south-central Texas (A.O.U. Check-list, 1957:181). Loetscher (1955:27) saw a flock of 39 curlews near Tamos on June 30, and he notes that nonbreeding birds are fairly common at all seasons in Veracruz. Similarly, the species is present throughout the year on the central Gulf coast of Texas (Hagar and Packard, 1952:8). Authors of the Mexican Check-list (1950:94) do not mention the possibility that birds of this species recorded in Mexico in July are summering rather than migrating. Twelve supposed migrants seen along Laguna Chila (Cacalilao), Veracruz, by Coffey (1960:291) on May 31, 1957, may have been summering birds.

=_Limosa fedoa_= (Linnaeus): Marbled Godwit.--Three were seen in shallow waters of the laguna at Camp 2 on July 9. Specimen: [M], 38919, testis 6 x 2 mm., fat, 305 gm., 6 P old, Camp 2, July 9. Probably our records were of nonbreeding birds, which are known to occur in summer elsewhere in Mexico (Mexican Check-list, 1950:94), sparingly in Texas (Hagar and Packard, 1952:8), and in South Carolina (A.O.U. Check-list, 1957:205). Apparently the only record for this species in Veracruz is one seen on May 11, 1954, east of Cacalilao (Coffey, 1960:292).

=_Tringa melanoleuca_= (Gmelin): Greater Yellowlegs.--Three birds were seen on alkaline flats at Camp 1 on July 7, and two were noted at Camp 2 on July 9. There is one previous report of this species in Tamaulipas, and, since it has been recorded as a migrant and winter resident in Mexico between July 26 and April 26 (Mexican Check-list, 1950:95), our records seem to pertain to unusually early autumnal migrants or, possibly, to nonbreeding, summering birds. Other mid-summer records are available from Tamos on June 30 and July 1, and the species is "to be expected every month of the year" in Veracruz (Loetscher, 1955:27). Sight records for Veracruz in May (Coffey, 1960:291) may well pertain to summering birds. There are northern-summer records for this species from Texas (Hagar and Packard, 1952:8), Surinam (Haverschmidt, 1955:367), and other areas within the winter range of this yellowlegs (A.O.U. Check-list, 1957:190).

=_Catoptrophorus semipalmatus semipalmatus_= Gmelin: Willet.--The Willet was common on the island. We found evidence of breeding and also saw large flocks of birds that were either nonbreeders summering in the area or early, postbreeding migrants from more northerly places. All along the beach and at the edge of the laguna at both camps we found Willets in twos or threes, often accompanied by one or two Black-bellied Plovers. On July 10 a small juvenile was captured; two adults in breeding plumage evidenced obvious concern at this action. On July 6 a flock of 30 birds flew east over Camp 1, and a flock of 90 was seen flying south over Camp 1 on July 7.

Specimens (7): [M], 38922, testis 6 x 1 mm., 264 gm., breeding plumage; [F], 38923, ova to 2 mm., 269 gm., breeding plumage; [F], 38924, ova to 1 mm., 280 gm., 3 P old; [F], 38925, ova to 1 mm., 319 gm.; [M], 38921, testis 7 x 2 mm., 211 gm., breeding plumage; Camp 1, July 7. Male, 38927, fat light, 231 gm., 4 P old, Camp 2, July 9. Juvenile, sex not recorded, 38920, 43.0 gm., 1 mile south of Washington Beach, July 10. Two of our specimens, both males, are in worn breeding plumage and evidence no molt; another specimen, a female, is also in breeding plumage but is molting on the breast. The remaining two adult skins in our series are three-quarters through the molt and are for the most part in fresh winter feather.

Dresser (1866:37) took an unspecified number of specimens of the Willet at the "Boca Grande" in July and August, but actual breeding in Tamaulipas was first established by C. R. Robins, who found a "scattered colony of breeding Willets" and took a female with an egg in the oviduct on May 9, 1949, near Tepehuaje (Sutton, 1950:135). Sutton (_op. cit._) has discussed the characters of this specimen and of birds from Cameron County, Texas. The specimen from Tepehuaje reportedly is closer to _C. s. inornatus_ than to _C. s. semipalmatus_ both in size and color, and birds from Cameron County are intermediate between the two subspecies in size but like _C. s. inornatus_ in color.

TABLE 3.--MEASUREMENTS IN MILLIMETERS OF SPECIMENS OF CATOPTROPHORUS SEMIPALMATUS FROM THE BARRIER ISLAND OF TAMAULIPAS

=============+======+======+========+========+======== SEX AND | | | | | Weight CATALOGUE | Wing | Tail | Full | Tarsus | in NUMBER | | | culmen | | grams -------------+------+------+--------+--------+-------- [M] 38921[A] | 197 | 80.6 | 61.0 | 59.0 | 211 [M] 38922[A] | 198 | 74.4 | 61.9 | 57.9 | 264 [M] 38927 | 194 | 75.5 | 60.4 | 56.4 | 231 [F] 38923[A] | 201 | 71.0 | 59.0 | 55.4 | 269 [F] 38924 | 199 | 71.0 | 61.3 | 59.0 | 280 -----------+------+------+--------+--------+--------

[Footnote A: Specimens in worn breeding plumage.]

Measurements of our five adults from the barrier island are presented in Table 3 for comparison with those of _C. s. semipalmatus_ and _C. s. inornatus_ given by Ridgway (1919:316-319). Like the specimens from Cameron County examined by Sutton (_op. cit._), our birds are intermediate in size between average-sized individuals of the two named subspecies. In color and pattern, we find that our specimens in breeding plumage fall within the range of variation of _C. s. semipalmatus_ as exemplified by five specimens in nearly identical states of wear and fading in the Museum of Natural History.

On the basis of the evidence presently available, we are reluctant to follow Sutton (1950:136) in assigning 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 analysis of geographic variation in this species, based, if possible, on proper segregation of age classes along the lines followed by Pitelka (1950) for _Limnodromus_, is obviously indicated.

PLATE 5

PLATE 6

=_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 x 1 mm., moderately fat, 107 gm., 4 P old; [M], 38932, testis 3 x 1 mm., moderately fat, 103 gm., molting; 75 miles south of Washington 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 class 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 assume breeding plumage, it is noteworthy that our specimens were molting from nuptial (summer) to winter plumage. None of the nonbreeding northern shorebirds 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 Washington Beach, July 8; 38 birds 73 miles south of Washington Beach, July 8; 29 birds 72 miles south of Washington 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 passes 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 x 1 mm., 325 gm., molting; [F], 38945, ovary small, 309 gm., in molt, brood patches refeathering; sex?, 38943, 315 gm., in molt; sex? 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 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): [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 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: [F], 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 ([M]?, 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 Tamos 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): [M], 38952, testis 4.5 mm., 150 gm., 8 P old; [M], 38955, testis 2 mm., 138 gm., 2 P old; [M], 38953, testis 5 x 1 mm., 142 gm., 5 P old; [F], 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): [M], 38958, testis 11 x 4 mm. (right testis 5 x 4 mm.), light fat, 45 gm., 6 P old; [M], 38959, testis 11 x 4 mm. (right testis 7 x 4 mm.), light fat, 45 gm., 6 P old; [F], 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.

=_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 x 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 x 3 mm., 455 gm., no brood patches, 8 miles south of Washington Beach, July 6. Male, 38962, testis 10 x 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 x 4.5 mm., 208 gm., 9 P old, 49 miles south of Washington Beach, July 8. Male, 38966, testis 8 x 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 x 23 mm. (abnormally large, possibly as a result of hemorrhage), 418 gm., brood patches refeathering; [M], 38969, testis 17 x 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 Tamos 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): [M], 38971, testis 5 mm., no fat, 62 gm., Camp 1, July 6. Male, 38972, testis 7.5 mm., no fat, 58 gm.; [M], 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.

Variation in _Chordeiles minor_ in Tamaulipas has recently been studied by Graber (1955). Two specimens taken by him on August 3, 1953, approximately 9 miles south of Carbonera, resemble birds from Terrell County, Texas, and represent _C. m. aserriensis_, as do our three birds from the barrier island. Two of Graber's specimens from Lomas del Real, in southeastern Tamaulipas, are distinctly darker and probably represent _C. m. neotropicalis_, a subspecies subsequently described from Chiapas (Selander and Alvarez del Toro, 1955).

=_Muscivora forficata_= (Gmelin): Scissor-tailed Flycatcher.--On July 7 near Camp 1, two individuals were found in stands of mesquite. One was taken and proved to be an adult male (38974, testis 6 x 3 mm., not fat, 40 gm.) in postnuptial molt (6 P old).

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): [M], 38981, testis 6 mm., 21.0 gm.; [M], 38977, testis 7.5 x 4 mm., not fat, 27.5 gm.; [M], 38979, testis 11 x 7 mm., 29.0 gm.; [F], 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: [F] 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).