Habitat Relationships and Life History of the Rota Bridled White-eye (Zosterops rotensis)

The Rota bridled white-eye (Zosterops rotensis)(Aves, Passeriformes) has experienced a severe population decline and range restriction over the last four decades. Little is known about this species and factors involved in the decline and range restriction are unclear. This study examined the potential roles of habitat alteration, introduced black drongos (Dicrurus macrocercus), and introduced rats in the decline and gathered more information on the behavior and breeding biology of this species. New life history data were collected and Rota and Saipan bridled white-eyes were found to differ in nest site characteristics and some behaviors. The importance of habitat alteration was assessed by examining Rota bridled white-eye habitat relationships at the microhabitat, within-range, Sabana-wide, and island-wide levels. Rota bridled white-eyes show a preference for high elevation wet forest but what drives their distribution within their current range was unclear. However, the alteration of this forest type by supertyphoon Roy in 1988 was probably the major factor in the decline of Rota BWEs between 1982 and 1996. Black drongo and Rota bridled white-eye relationships were addressed using current and historical survey data. Black drongos were found to prey on Rota bridled white-eyes but they probably only played at most a partial role in the decline of the Rota bridled white-eye. Introduced rats densities were assessed in Rota bridled white-eye areas and on other areas of the island and no evidence for rat numbers limiting Rota bridled white-eyes to their current range was found.