Population status of the Tinian Monarch (Monarcha takatsukasae) on Tinian, Commonwealth of the Northern Mariana Islands

We conducted surveys to evaluate the current population status of the Tinian Monarch (Monarcha takatsukasae), an insectivorous forest bird restricted to the island of Tinian, Commonwealth of the Northern Mariana Islands. In 1996, we recounted transects surveyed in 1982 and used the same analysis procedure to compare 1982 and 1996 population estimates. The 1996 population estimate was 55,721 ± 3,846 SE (48,345–63,495 95% CI), which is 57% higher than our estimate of 35,846 ± 2,211 SE (31,668–40,337 95% CI) for 1982. Vegetation density, measured by canopy cover and lateral visibility at each station, has also increased since 1982. Our data suggest that the Tinian Monarch population has increased possibly due to increased habitat availability, but remains at risk both from an accidental introduction of brown tree snakes (Boiga irregularis) to the island and stochastic processes.