Lives in colonies. Densities vary greatly. Peak densities reach 750 or more individuals per ha (Lidicker 1966). Peaks in abundance (irruptions) occur late summer-fall in Hawaii (Tomich 1986). Home range is less than an acre.
On western Mauna Kea, Hawaii, Amarasekare (1994) found no evidence that this species preys on eggs, young, or adults of endemic birds.