Status of Forest Birds on Tinian Island, Commonwealth of the Northern Mariana Islands, with an Emphasis on the Tinian Monarch (Monarcha takatsukasae) (Passeriformes; Monarchidae)

Abstract

Landbird populations on Tinian Island have been periodically surveyed since 1982 to evaluate the status of non-native and native landbirds. We report the results of surveys in 2013 and the observed changes during 31 years in species population trends based on surveys since 1982. A total of 11 native and 3 non-native species were detected during the 2013 survey. Population sizes were estimated using point-transect distance sampling methods, and population trends were assessed using repeated measures analysis of variance for nine forest bird species. In all years, the Rufous Fantail (Rhipidura rufifrons) and Bridled White-eye (Zosterops conspicillatus) were the most abundant species, whereas the White-throated Ground Dove (Pampusana xanthonura) was the least abundant species in 1982, 1996, and 2008, and the Mariana Kingfisher (Todiramphus albicilla) was the least abundant in 2013. The less common species numbered in the low thousands included the Mariana Fruit Dove (Ptilinopus roseicapilla), White-throated Ground Dove, introduced Philippine Collared Dove (Streptopelia dusumieri), Mariana Kingfisher (Todiramphus albicilla), and Micronesian Myzomela (Myzomela rubratra). The Micronesian Starling (Aplonis opaca) and Tinian Monarch (Monarcha takatsukasae) were estimated to number in the tens of thousands. The most abundant species were the Rufous Fantail, numbering more than 100,000, and the Bridled White-eye, numbering more than 400,000. The overall trends in abundance between 1982 and 2013 showed an increase in the Mariana Kingfisher, Micronesian Starling, Rufous Fantail, White-throated Ground Dove, and Philippine Collared Dove, while populations were stable for the Bridled White-eye and Tinian Monarch. Declines were seen for the Mariana Fruit Dove and Micronesian Myzomela. These trends matched previous analyses with the exception that Tinian Monarch abundance showed an increase in the 2013 survey.