Part 56

Black-naped Tern

Sterna Sumatrana Raffles, Trans. Linn. Soc. London, 13, pt. 2, 1822, p. 329. (Type locality, Sumatra.)

Sterna melanauchen Kittlitz, Obser. Zool., in Lutké, Voy. "Le Séniavine," 3, 1836, pp. 306, 308 (Guahan, Ouleai); Hartlaub and Finsch, Proc. Zool. Soc. London, 1872, pp. 90, 113 (Pelew, Uap); Gräffe, Journ. Mus. Godeffroy, 2, 1873, p. 123 (Yap); Finsch, Journ. Mus. Godeffroy, 8, 1875, pp. 5, 41 (Palau); idem, Ibis, 1880, pp. 220, 330, 332 (Taluit); idem, Journ. f. Ornith., 1880, p. 295 (Ponapé); idem, Proc. Zool. Soc. London, 1880, p. 577 (Ruk); idem, Ibis, 1881, pp. 113, 115 (Ponapé); Schmeltz and Krause, Ethnogr. Abth. Mus. Godeffroy, 1881, pp. 281, 299, 330, 353 (Ponapé, Mortlock, Nukuor, Ruk); Salvadori, Ornith. Papuasia, 3, 1882, p. 444 (Pelew, Mackenzie, Ruk, Ponapé, Marshalls); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 74 (Pelew, Uap, Ruk, Luganor, Nukuor, Ponapé, Taluit); Sanders, Cat. Birds British Mus., 25, 1896, p. 126 (Carolines, Pelews, Marshalls); Nehrkorn, Kat. Eiers., 1899, p. 222 (Palau); Hartert, Novit. Zool., 7, 1900, p. 10 (Ruk); Schnee, Zool. Jahrbücher, 20, 1904, p. 390 (Marschall-Inseln); Takatsukasa and Kuroda, Tori, 1, 1915, p. 52 (Ruk, Ponapé); Uchida, Annot. Zool. Japon., 9, 1918, pp. 483, 488 (Ponapé).

Sterna sumatrana Wetmore, in Townsend and Wetmore, Bull. Mus. Comp. Zoöl., 63, 1919, p. 186 (Arhno).

Gygisterna sumatrana Kuroda, in Momiyama, Birds Micronesia, 1922, p. 52 (Pelew, Mackenzie, Yap, Ruk, Luganor, Nukuor, Ponapé, Taluit, Arhno).

Gygisterna sumatrana sumatrana Kuroda, Avifauna Riu Kiu, 1925, p. 192 (Carolines, Pelews).

Sterna sumatrana sumatrana Yamashina, Tori, 7, 1932, p. 410 (Aruno); Hachisuka, Birds Philippines, 2, 1932, p. 335 (Caroline, Pelew); Hand-list Japanese Birds, rev., 1932, p. 195 (Palau, Guam, Saipan, Yap, Truk, Lukunor, Nukuoro, Ponapé, Jaluit, Namu, Arhno, Majuro, Aurh); Peters, Check-list Birds World, 2, 1934, p. 336 (Caroline Islands); Mayr, List New Guinea Birds, 1941, p. 36 (Micronesia); Hand-list Japanese Birds, 3d ed., 1942, p. 218 (Babelthuap, Koror, Yap, Truk, Lukunor, Nukuoro, Ponapé, Jaluit, Namu, Arhno, Majuro, Aurh); Mayr, Birds Southwest Pacific, 1945, p. 24 (Micronesia); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 55 (Peleliu, Ulithi).

Geographic range.--Micronesia, central Polynesia, northern Australia, Malaysia, west to India, and north to the Riu Kiu Islands. In Micronesia: Palau Islands--Babelthuap, Koror, Peleliu; Caroline Islands--Yap, Ulithi, Truk, Lukunor, Nukuoro, Ponapé; Marshall Islands--Jaluit, Namu, Majuro, Aurh, Bikini.

Characters.--Adult: A small tern with a long, forked tail and white plumage often with pinkish cast except for mantle, back, rump, tail, wing-coverts, and scapulars which are pale pearl-gray; band across nape, spot in front of eye, and outer web of outer primary black; bill and feet black.

Immature: Resembles adult, but black and white mottling on upper parts.

Measurements.--Measurements are listed in table 19.

Specimens examined.--Total number, 15 (8 males, 6 females, 1 female?), as follows: Palau Islands, AMNH--exact locality not given, 4 (Oct.-Dec.); Caroline Islands, USNM--Ulithi Atoll, 6 (Aug. 15, 16, 20, 22); AMNH--Truk, 1 (Feb. 10); Marshall Islands, USNM--Bikini, 4 (March 26, April 30).

Nesting.--Nehrkorn (1899:222) recorded eggs taken at the Palau Islands. Yamashina (1932a:410) listed the finding of three nests containing one egg each on September 26, 1931, at Arhno in the Marshall Islands. The NAMRU2 party obtained no evidence of nesting at Ulithi or Palau in August and September, 1945. Coultas (field notes) obtained reports of the finding of two eggs at the Palau Islands in the period October to December, 1931.

Parasites.--Uchida (1918:483, 488) records the following Mallophaga taken at Ponapé from this tern: Docophorus albemarlensis, Colpocephalum milleri, and Colpocephalum impertunum.

Remarks.--There are no records for the Black-naped Tern from the Mariana Islands, although the species is known from the Palau, Caroline and Marshall Islands. At Ulithi Atoll, the NAMRU2 party observed these terns at the islands of Potangeras, Mangejang, Pau, and Losiep in August, 1945. They were found in groups of 4 to 15, either sitting on sandy beaches or rocky exposures or flying over the reefs. Unlike the Crested Tern, these birds appeared quite unafraid of man and would hover over a freshly killed or wounded individual of their own kind, making of themselves easy targets. The writer saw only one Black-naped Tern at the Palau Islands (Peleliu, on September 16, 1945). The birds seem to prefer the "low" atolls to the "high" volcanic islands of Micronesia.

Two subspecies of Sterna sumatrana are recognized by Peters (1934:336): Sterna sumatrana mathewsi known from islands of the western Indian Ocean and Sterna s. sumatrana from islands of Oceania, Australia, Malaysia, and China coast. There is a considerable area separating these subspecies. For populations in the Pacific area, other names which have been proposed are Sterna sumatrana kempi Mathews for birds from Torres Straits and Gygis decorata Hartlaub for birds from the Fiji Islands. A study of 201 specimens of this species from various parts of its range (in the collections of the American Museum of Natural History and the United States National Museum) shows that there is little color variation within the species. This observation is the same as that of Mathews (1912:372).

As listed in table 19, measurements of the length of the wing show little variation. The length of the tail of birds from localities more remote from the continent of Asia (Micronesia, Phoenix, Union, Fiji, Samoa, Tonga, and the islands of the Indian Ocean: Aldabra and Providence) is, on the average, shorter than the length of the tail of birds from islands nearer the Asiatic mainland. This shortness is reflected also in the measurement of the difference between the shortest and longest tail feather.

TABLE 19. MEASUREMENTS OF SPECIMENS OF Sterna sumatrana

Columb headings:

A: No. B: Wing C: Tail D: Difference: Longest and shortest tail feather E: Exposed culmen F: Tarsus

===================+===+=========+=========+=======+==========+========== LOCALITY | A | B | C | D | E | F -------------------+---+---------+---------+-------+----------+---------- S. s. sumatrana | | | | | | Micronesia | 13| 221 | 127 | 65 | 37 | 20.5 | | 211-225 | 117-138 | 54-79 | 35-39 | 20.0-21.0 | | | | | | Phoenix and Union| 5| 228 | 113 | 66 | 37 | 19.5 | | | | | 36-38 | 18.5-20.0 | | | | | | Fiji, Samoa, | 29| 221 | 131 | 63 | 38 | 20.0 Tonga | | 218-229 | 122-142 | 51-74 | 36-41 | 18.0-21.0 | | | | | | New Caledonia, | 8| 224 | 141 | 72 | 39 | 19.5 Loyalty, New | | 221-230 | 135-148 | 68-81 | 37-41 | 18.5-20.0 Hebrides | | | | | | | | | | | | Queensland, | 4| 229 | 142 | 78 | 38 | 19.5 Torres Straits | | | 139-148 | 71-83 | 36-40 | 18.5-20.0 | | | | | | Solomons | 52| 227 | 144 | 77 | 36 | 19.0 | | 220-232 | 129-162 | 66-95 | 34.0-38.5| 18.5-20.5 | | | | | | New Guinea, | 10| 224 | 143 | 76 | 34 | 19.5 Bismarcks | | 219-231 | 135-146 | 67-81 | 32.0-36.5| 18.5-20.0 | | | | | | Malay area | 49| 228 | 141 | 74 | 34 | 20.0 | | 220-234 | 125-153 | 63-84 | 32.0-37.0| 19.0-20.5 | | | | | | China coast, | 21| 223 | 144 | 77 | 35 | 19.5 Riu Kiu | | 212-234 | 130-151 | 67-85 | 31.5-38.0| 19.0-20.0 | | | | | | S. S.mathewsi | | | | | | Indian Ocean: | 10| 220 | 125 | 71 | 38 | 19.0 Aldabra, | | | | | 35.0-40.0| 18.0-20.0 Providence | | | | | | -------------------+---+---------+---------+-------+----------+----------

The differences in the length of the exposed culmen of these terns shows that birds from islands more remotely oceanic possess longer bills than do those from islands closer to the Asiatic continent. Murphy (1938:538) has written that this phenomenon is characteristic among some species which have both continental and insular populations (or subspecies). Figure 10 shows the southeastern part of the range of the subspecies, Sterna s. sumatrana, and gives the average measurements of the exposed culmen of birds from several localities. These localities are given in table 19. Terns with longer bills (37-39) were taken in Micronesia, in the Polynesian islands, and in northern Australia. Terns with shorter bills (34-36) were taken in Melanesia, Malaysia, and the coastal region of China, but there appears to be no abrupt line of demarkation between them. Further evidence of this tendency may be obtained from the literature. Kuroda (1925:191) gives the measurements of the exposed culmen of seven males and five females from the Riu Kius as averaging 35 mm. (range 31-40.5). It is also of interest to note that the length of the exposed culmen of the males averages one to two mm. longer than that of the females. The status of Sterna sumatrana mathewsi may be questioned. I find no characters separating my series of mostly poor specimens. The systematic position of this subspecies from the Indian Ocean (and likewise the status of subspecies of other sea birds which range into the Indian Ocean) may not be known with certainty until additional material is obtained.

=Sterna lunata= Peale

Spectacled Tern

Sterna lunata Peale, U. S. Expl. Exped., 8, 1848, p. 277. (Type locality, Vincennes Island, Paumotu Group.)

Sterna lunata Hartlaub, Proc. Zool. Soc. London, 1867 (1868), p. 831 (Pelew); Hartlaub and Finsch, Proc. Zool. Soc. London, 1868, pp. 9, 118 (Pelew); idem, Proc. Zool. Soc. London, 1872, pp. 90, 113 (Pelew); Finsch, Journ. Mus. Godeffroy, 8, 1875, pp. 5, 41 (Palau); Saunders, Cat. Birds British Mus., 25, 1896, p. 100 (Pelew); Takatsukasa and Kuroda, 1, 1915, p. 62 (Ruk, Pelew); Hand-list Japanese Birds, rev., 1932, p. 195 (Palau); Hand-list Japanese Birds, 3d ed., 1942, p. 218 (Palau); Mayr, Birds Southwest Pacific, 1945, p. 26 (Micronesia).

Onychoprion lunatus Salvadori, Ornith. Papuasia, 3, 1882, p. 451 (Pelew); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 76 (Pelew).

Melanosterna lunata Kuroda, in Momiyama, Birds Micronesia, 1922, p. 52 (Pelew).