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 |
[A] Common Tern, Forster Tern, and Long-billed Curlew also seen but not counted.
[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° 26´ North and 93° 30´ West.