The proposed Tinian Island IBA encompasses the majority of the island, excluding a small settlement in the southern part of the island and including a large military leasehold area in the north. Part of the military leasehold area is designated a National Historical Site. The military leasehold areas are used for training exercises, but are uninhabited. The proposed IBA includes the Hagoi Marsh and Marpo Swamp areas, which are important as water sources and as animal habitat.
Engbring et al. (1986) reported that the Tinian Monarch, endemic only to Tinian, was present in every surveyed habitat in Tinian. The USFWS (2005) also found that the Tinian Monarch inhabited a variety of forest habitats, including native, secondary, and introduced vegetation. Engbring et al. (1986) also found that other native birds were distributed throughout the island. Engbring et al. (1986) found that the northern part of Tinian, the location of Hagoi marsh, held the largest population of monarchs and was important for wetland birds, including the US federally listed and protected Mariana Common Moorhen. Tanaka and Haig (2004) found that Mariana Common Moorhens appear to use Tinian’s Lake Hagoi, particularly during the dry season. Wiles et al. (1985) and O’Daniel and Krueger (1999) found the Micronesian Megapode on Tinian. O’Daniel and Krueger (1999) reported sightings of the Megapode were made at Maga, Upper Mt. Lasu, and Bateha, all sites with native limestone forest. These sites are located on the center escarpment of the island. Native forest is also found on the eastern part of the island in Unai Dankulo (NPS, 2001). Reichel (1991) reported over 270 pairs of breeding seabirds on Tinian, including 150 pairs of White Terns.
Pressure/threats to key biodiversity
The island is inhabited and development projects are planned to increase tourism. The military also plans to increase and intensify use of the military leasehold areas. Grazing by goats and cattle has disturbed much of the island’s vegetation, most of which is introduced. There have been a few credible sightings of the Brown Treesnake on Tinian, although there is no evidence of an established population. Rats pose a current threat.
There are no formal protective mechanisms, although the military must ensure the integrity of the National Historical Site and natural features of the area. There are some local, small conservation areas on Tinian, such as the Airport Mitigation Site, a small conservation area in the southwest corner of the island established for Tinian Monarchs, and a small mitigation area in the central part of the island (A. Marshall, pers. comm.).
Habitat and land use
The northern two-thirds of Tinian Island are owned by the CNMI and under lease to the US Department of Defense. The southern third of Tinian is home to the town of San Jose with a population of approximately 4000 people. In 2001 there were plans to build additional hotels and expand tourism through construction of a casino. This report thus recommended excluding the town from the IBA, although birds do use its urban areas. Native forest is found in patches scattered throughout Tinian, including in the military lease area and in the southeast corner of the island; thus, the majority of the island was selected as a proposed IBA. Unai Dankulo on the eastern part of the island has native forest, and Lake Hagoi, on the northwestern part of the island, is a rare wetland area. The central escarpment, with patches of native forest, runs down the middle of the island. Rather than select many IBAs to capture the scattered native habitats, this report recommended one IBA for the majority of the island of Tinian.
BirdLife International (2022) Important Bird Areas factsheet: Tinian Island. Downloaded from
http://www.birdlife.org on 25/09/2022.