Mariana Crow

The Mariana crow is a small black crow with a bluish-black gloss on its tail, and a greenish-black gloss on its back, underparts, head, and wings. In general, females are smaller than males. An adult weighs about 9 ounces (260 g) and is about 15 inches (38 cm) long. The Mariana crow has a variety of vocalizations, including two locational calls used to maintain contact between pairs, family members and flock mates. These locational calls are either a high-pitched series of one to three caw or hi sounds, or a series of longer caw sounds with a nasal aaa element to the call; the latter call may be used exclusively between mated pairs. Alarm calls are a rapid series of sharp caws. The birds also make a variety of squalling, guttural sounds, which may be done either quietly or excitedly.

The Mariana crow inhabits second growth and mature forests, as well as coastal strand vegetation, but nests only in native limestone forest. It preferentially nests in the crowns of two canopy-emergent tree species: yoga tree (Elaeocarpus joga) and the fig Ficus prolixa. The crow currently is only found on the island of Rota. It disappeared from southern Guam in the 1960s and from central Guam in the 1970s, mostly inhabiting Andersen Air Force Base. Its population on Rota has also decreased.

Diet. Extremely versatile, the Mariana crow is an opportunistic omnivore, feeding on insects, lizards, other birds' eggs, hermit crabs, fruits, and seeds.

Nesting. The Mariana crow begins nesting as early as July and as late as May. The nest is a large, cupped platform of small sticks, lined with leaf fibers. Clutch size varies from 1 to 4 eggs, and both parents incubate the eggs, brood the chicks, and care for the juveniles even after they fledge. Parental care has been known to range from 5 to 18 months, and juveniles may take as long as 3 years before entering the adult breeding cycle.