Part 90

Characters.--Adult: A small, black crow with a slight greenish-black gloss on head; back, wings, and tail with bluish-black gloss; underparts with dull, greenish-black gloss; bases of feathers light grayish, more nearly white on neck, producing a somewhat ragged appearance; nasal bristles short but extending over nostrils and base of culmen; bill and feet black; iris dark brown. Female smaller.

Immature: Resembles adult, but feathers with less gloss; wings and tail browner.

Measurements.--Measurements of Corvus kubaryi are listed in table 35.

Weights.--The NAMRU2 party obtained weights of the Marianas Crow as follows: from Guam, 5 males, 231-270 (256), 11 females, 205-260 (242); from Rota, 1 male, 256; 1 female, 260 grams.

TABLE 35. MEASUREMENTS OF Corvus kubaryi

=========+===========+===========+===========+=========+========= | Number | | | Full | LOCATION | and sex | Wing | Tail | culmen | Tarsus ---------+-----------+-----------+-----------+---------+--------- Guam | 9 males | 236 | 165 | 55 | 51 | | (229-244) | (158-170) | (51-57) | (49-52) | 19 females| 227 | 151 | 50 | 50 | | (222-241) | (143-166) | (47-54) | (46-54) | | | | | Rota | 3 males | 235 | 167 | 54 | 50 | | (233-236) | (166-169) | (53-56) | (49-51) ---------+-----------+-----------+-----------+---------+---------

Specimens examined.--Total number, 49 (20 males, 27 females, 2 unsexed), as follows: Mariana Islands, USNM--Guam, 26 (May 25, 29, June 4, 7, 8, 9, 18, 28, 29, July 10, 12, 18, Sept. 5, 11)--Rota, 4 (Oct. 22, 25, 29); AMNH--Guam, 19 (Jan., Feb., March, Aug., Sept., Dec.).

Nesting.--In the spring of 1945, the NAMRU2 party obtained records of nesting activities by crows. One nest was observed on March 8 in a banyan tree. Specimens collected from May to September were not in breeding condition, and it is thought that the nesting period is concentrated in the winter and spring months. Watson (1946:41) reports finding a young crow being fed on May 8 by an adult.

Molt.--The Marianas Crow molts in the period from May to August or September. Most of the birds taken by the NAMRU2 party in this period were in the process of molt. Skins obtained at Rota in late October also exhibit signs of molt. Specimens taken in December, January and February are in fresh or slightly worn plumage. The crow presents an exceedingly shabby appearance in molt, because the grayish and whitish basal parts of the feathers are exposed.

Food habits.--The crow is an omnivorous feeder. Stomachs examined contained both plant and animal food. Both Seale (1901:55) and Safford (1905:79) comment on the damage which the crow does to the corn crop at Guam. Seale remarks that the crow has a reputation for plundering nests of other birds. The NAMRU2 party saw crows being chased by starlings on several occasions.

Parasites.--Wharton (1946:174) obtained the chigger (Acarina), Trombicula sp., from the crow at Guam.

Remarks.--The Marianas Crow is confined to the forested areas and to the coconut plantations at Guam. The birds were seen as singles or in small flocks, often along the roadways. In a count of the number of birds seen along the roadways of Guam, the author (1947:124) found crows to constitute 2.4 per cent of the total population of birds counted and observed the crow on 21.6 per cent of the 125 roadway counts made. Coultas (field notes) noted the birds at the northern part of Guam. The NAMRU2 party found the birds distributed in most parts of the island but usually they were infrequent near areas where large numbers of service personnel were stationed. The birds were often noisy when flying in small flocks or in pairs; Seale (1901:55) also notes this. When observed in jungle areas, the birds were generally quiet, feeding and perching in dense foliage. At Rota, the NAMRU2 party found the bird to be fairly numerous and with habits resembling those of the crow at Guam. No differences in color or structure could be found between the specimens of crows obtained at the two islands.

Kittlitz (1836:305) was the first person to write an account of the crow at Guam. He called it Corvus solitarius and remarked that he later found the same species in the Philippines. Wiglesworth (1891a:46) also considered the crow at Guam to resemble one found in the Philippines and called it Corone phillipina. Later Reichenow named the bird Corvus kubaryi with the type locality as the Palau Islands. This locality proved to be erroneous and the bird was judged to be from Guam by Hartert (1898:59), who did not use the name C. solitarius because it was a nomen nudum, and recognized C. kubaryi as the correct name.

Evolutionary history of Corvus kubaryi.--Meinertzhagen (1926:59) writes that "Environmental influences seem to be mainly, if not entirely, responsible for geographic differences in the genus Corvus." Such may be the case in C. kubaryi, which is a small, dull-colored crow with a relatively unmodified bill. In structure, it has little resemblance to other crows found in the Pacific area. Kittlitz was the first to note a resemblance between the bird at Guam and one in the Philippines. Oustalet (1896:70) wrote that the bird at Guam is related to crows of the Moluccas and New Guinea. Although not closely related to the Hawaiian Crow, C. tropicus, both have little gloss on their feathers, a character which is common to many of the insular populations of crows. Mayr (1943:46) is of the opinion that the Hawaiian bird was derived from a North American ancestor, although Bryan (1941:187) suggests that it is related to C. macrorhynchus of southeastern Asia and remarks that the Hawaiian Crow, "has some relation to the Guam Crow." In looking for the ancestral stock of C. kubaryi, the several species of crows which occur to the north, west and south of the Marianas have been examined. In size and general structure, C. kubaryi appears to be closest to the C. enca group, and not as closely related to the C. macrorhynchus group. The small size, the shape of the culmen, the lack of pointed feathers on the breast, and the presence of white on the basal parts of the feathers of the nape are characters which C. kubaryi has in common with C. enca. Nasal bristles cover the frontal base of the culmen in C. kubaryi; this character is found also in C. enca florensis. C. kubaryi differs from the C. enca group by lacking the purple sheen on the upper parts; this sheen is conspicuous in the latter species. C. kubaryi appears to have little in common with C. meeki of the Solomons and C. orru of the Moluccas and New Guinea area. There is apparently no close relation between the Marianas Crow and the crow which reaches the Bonins. The latter crow, according to the Hand-list of Japanese Birds (Hachisuka et al., 1932:1), is called C. coronoides hondoensis Momiyama and is apparently now extinct in the Bonins.

In summary, it may be said that C. kubaryi is an isolated and modified species of crow, which probably has been living at Guam and Rota for a considerable length of time. Whether it once lived on other islands in Micronesia is unknown, but it is entirely possible that the present population may represent a remnant of one which formerly had a more extensive distribution. The characters which show its distinctness from possible ancestral species include its small size, its slender bill, and its dull coloration. It is thought to have been derived from the C. enca group, C. e. pusillus of the Philippines or C. e. celebensis of the Celebean area.

=Luscinia calliope calliope= (Pallas)

Siberian Rubythroat

Motacilla Calliope Pallas, Reise durch versch. Prov. russ. Reichs, 3, 1776, pp. 261, 325, 697. (Type locality, Yenesei.)

Luscinia calliope calliope Hand-list Japanese Birds, rev., 1932, p. 178 (Koror); Hand-list Japanese Birds, 3d ed., 1942, p. 197 (Koror); Mayr, Birds Southwest Pacific, 1945, p. 302 (Palau).

Geographic range.--Breeds in northeastern Asia. Winters south to Malaysia. In Micronesia: Palau Islands--Koror.

Remarks.--The Siberian Rubythroat is considered to be a casual winter visitor to the Palau Islands.

=Monticola solitaria philippensis= (Müller)

Chinese Blue Rock Thrush

Turdus philippensis Müller, Natursystem Supplements- und Register-Band, 1776, p. 145. (Type locality, Philippine Islands, ex Buffon.)

Monticola philippensis philippensis Hand-list Japanese Birds, rev., 1932, p. 177 (Koror); Mayr, Birds Southwest Pacific, 1945, p. 302 (Palau).

Monticola solitarius philippensis Hand-list Japanese Birds, 3d ed., 1942, p. 197 (Koror).

Geographic range.--Breeds in northeastern Asia and Japan. Winters south to Malaysia. In Micronesia: Palau Islands--Koror.

Remarks.--The Chinese Blue Rock Thrush is apparently an infrequent winter visitor to the Palau Islands.