Bridled White-eye Zosterops conspicillatus Scientific name definitions

The Bridled White-eye, or Nosa' in the Chamorro language, is one of the better-studied bird species of the Mariana Islands. Nonetheless, there have been limited studies on this species for the past 20 years beyond population surveys. In addition to periodic studies into its population status, trends, and dynamics, there has been research on its foraging ecology, microhabitat use, social behavior, and breeding biology, but many gaps in our knowledge remain.

A member of the widespread African-Australasian Zosterops genus, the Bridled White-eye has among the highest population densities of any bird species. Flocks of 50 or more individuals, which in many cases are members of family groups, occupy home ranges, but pairs do not defend all-purpose territories. Within home ranges, individuals are supremely versatile foragers and users of habitat, although they are principally gleaners of insects present in the outer canopy of forests. Population densities are by far the greatest in native forest, although birds also occupy a variety of disturbed wooded habitats and even areas of human habitation. Evidence suggests that, although breeding occurs year-round, nesting peaks in the dry season from winter to spring.

The Bridled White-eye is known historically from the islands of Saipan, Tinian, and Aguiguan, although a separate subspecies, now extinct, once occurred on Guam. Although still abundant, the species is threatened with further extirpation by the possible introduction of the brown tree snake (Boiga irregularis) on other islands—a non-native predator that is responsible for the extinction of the Guam population. To aid in its conservation, the Bridled White-eye has been translocated to the more northerly, uninhabited Mariana Island of Sarigan, where it is prospering. More recent conservation initiatives have expanded to include translocation to Guguan Island.