Observations on the Behavior and Ecology of the Mariana Crow

Abstract

The Mariana Crow (Corvus kubaryz? is found on the islands of Guam and Rota in the Mariana Islands of Micronesia. An attractive, fairly tame island inhabitant, the Mariana Crow is small with short, broad wings, a green gloss to the black head plumage, and a blue gloss to the black body plumage. Patches of gray feather bases in the body plumage and white feather bases in the neck region are often exposed. The bill and feet are black, eyes are brown, and nasal bristles are prominent. As in other corvids, the juveniles have short, flutTy head plumage. In addition, young Mariana Crows are disheveled in appearance; exposed feather bases on the breast show as light patches, the black plumage has a brown cast, and flight feathers may appear worn at the tips. As suggested by Baker (195 I), C. kubaryi may be closely related to C. enca of the Malayan and Philippine regions. He further speculates that “C. kubarvi is an isolated and modified suecies of crow, which probably has been living at Guam and Rota for a considerable length of time.” Features which differ from the candidate ancestral species include small size, slender bill, and dull coloration. Goodwin (1976) believes, however, that aside from the geographic proximity of C. enca, any Corvus species could be ancestral. The Mariana Crow is a little-known species whose populations have suffered declines over the past 25 years. In 1975, the crow was placed on the Trust Territory Endangered Species list; in 1984, it was placed on the U.S. Federal Endangered Species List along with the Bridled Whiteeye (Zosterops c. conspicillatus), Guam Flycatcher (Myiagra freycineti), Micronesian Kingfisher (Halcyon c. cinnamomina), Vanikoro Swiftlet (Aerodramus vanikorensis bartschii), Common Moorhen (Gallinula chloropus guamI>, and Guam Rail (Rallus owstoni; revised nomenclature, Pyle and Engbring 1985). Although a recovery plan for