Specimens (7): ♂, 38922, testis 6 × 1 mm., 264 gm., breeding plumage; ♀, 38923, ova to 2 mm., 269 gm., breeding plumage; ♀, 38924, ova to 1 mm., 280 gm., 3 P old; ♀, 38925, ova to 1 mm., 319 gm.; ♂, 38921, testis 7 × 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 Catalogue Number | Wing | Tail | Full culmen | Tarsus | Weight in grams |
|---|---|---|---|---|---|
| ♂ 38921[A] | 197 | 80.6 | 61.0 | 59.0 | 211 |
| ♂ 38922[A] | 198 | 74.4 | 61.9 | 57.9 | 264 |
| ♂ 38927 | 194 | 75.5 | 60.4 | 56.4 | 231 |
| ♀ 38923[A] | 201 | 71.0 | 59.0 | 55.4 | 269 |
| ♀ 38924 | 199 | 71.0 | 61.3 | 59.0 | 280 |
[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.
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