Shyer than most crows species, the Mariana crow is usually well-concealed amongst the foliage of its forest habitat (2). This species forages in the canopy, the understorey and on the ground, and takes a variety of food items, including fruits, seeds, buds, as well as small lizards, immature mammals, bird eggs and invertebrates (2). When searching for live prey, the Mariana crow rustles through the leaf litter and tears at bark to expose insects (5).
The Mariana crow forms family groups consisting of a monogamous pair and one to three offspring, although large social aggregations occasionally form. Breeding is believed to occur throughout the year on Rota, with peak nesting activity occurring from August to February. On Guam, recent observations have only recorded nesting between October and mid-April. Both parent birds contribute to all aspects of breeding, though incubation is primarily carried out by the female (5). The nest is constructed over a period of around one week, after which, a clutch of one to four eggs is laid and incubated for 21 to 23 days (4) (5). The offspring remain in the nest for 36 to 39 days, but continue to receive parental care for a remarkably long period, ranging between three and 18 months (5).