Species Status Assessment Report for the Tinian Monarch (Monarcha Takatsukasae)
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Tinian Monarch SSA Version 1.0 Species Status Assessment Report for the Tinian Monarch (Monarcha takatsukasae) Tinian Monarch nest at the Santa Lourdes Shrine, March 2007. Photo by Eric VanderWerf U.S. Fish & Wildlife Service Pacific Islands Fish and Wildlife Office Version 1.0 March 2018 1 Tinian Monarch SSA Version 1.0 Suggested citation: U.S. Fish and Wildlife Service. 2018. Species status assessment for the Tinian Monarch. Version 1.0, March 2018. U.S. Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office, Honolulu, HI. 2 Tinian Monarch SSA Version 1.0 Executive Summary Introduction The Tinian Monarch is a small flycatcher bird endemic to the 39-mi2 (101 km2) island of Tinian, the second largest island in the Commonwealth of the Northern Mariana Islands (CNMI), in the western Pacific Ocean. In 1970, the United States Fish & Wildlife Service (Service) listed the Tinian Monarch as an endangered species under the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq). In 1987, the Service downlisted the Tinian Monarch to a threatened status, and in 2004, it was removed from the list of threatened species. In 2013, the Service was petitioned to list the Tinian Monarch as an endangered or threatened species under the Act, and as a result, the Service began a full review of the species’ status using the Species Status Assessment (SSA) approach. The SSA will serve as the foundational science for informing the Service’s decision whether or not to list the Tinian Monarch. This SSA report assesses the species’ ecology, current condition, and future condition under various scenarios. The Tinian Monarch is an arboreal bird that inhabits forested areas of the island. The forest on Tinian is broadly divided into three types—native (limestone), secondary-mixed, and tangantangan (Leucaena leucocephala), which together comprises approximately 64% of the island’s land cover. Studies of the ecology and life history of the bird indicate that while the Tinian Monarch thrives in all three forest types, its ecology and behaviors do vary among the forests. Specifically, the Monarch lives in higher densities in the native forest, which comprises approximately 8% of the island’s forest cover (5% of the total land cover), and also has a higher nesting rate, density, and success in this forest. We have identified the basic needs of individuals and for the population and species as a whole as follows: Individual Needs • Shelter, prey for foraging (insects), and breeding sites, all of which are provided by forest habitat of sufficient density. 3 Tinian Monarch SSA Version 1.0 Population/ Species Needs • Forest habitat of sufficient area and continuity to accommodate home range and breeding territories. • Forest habitat continuity / connectivity to accommodate island-wide population distribution and dispersal. • Low abundance of existing predators and prevention of the establishment of new, invasive predators like the brown treesnake. Executive Summary – Current Condition Historically, human activities have drastically altered Tinian’s landscape including the amount of forest habitat on the island available to the Monarch. Impacts to the forests of Tinian began with the arrival of the original Chamorro people 3,000-4000 ago and increased following European colonization in the 1500s. By the conclusion of the Second World War (WWII), human activities on the island had seriously reduced what was originally extensive native forest habitat to tiny remnants. Following the end of WWII and until the 1990s, there was a steady and significant regrowth of forest with some periodic fluctuations in total forest cover, accompanied by substantial change in composition. Beginning in the 1980s through a long-term lease with the CNMI government, the United States Navy (U.S. Navy) has occasionally conducted exercises of variable scale (up to 2,000 personnel (U.S. Pacific Command 1999, pp. 2-11, 3-37)) in the northern two-thirds of Tinian and involving occasional use of WWII structures and clearing of tangantangan from old runways. Today, most (approximately 92%) of the forest on Tinian is comprised of mixed-secondary vegetation and the invasive tangantangan. During the aforementioned loss of forest habitat which began with the arrival of human settlers to the island and culminating with the largest extent of forest reduction preceding and during the WWII, the Tinian Monarch population had experienced a drastic decline, possibly less than 80% of the current population level. Since the end of WWII, the Monarch population has increased to a current population size of almost 100,000 individuals in conjunction with a substantial rebound in forest growth. This exemplified the highly resilient nature of the Tinian Monarch in the face of drastic changes to the habitat upon which it depends. Currently, periodic forest habitat loss alone is not having a significantly measurable impact to the overall condition of the species. In 4 Tinian Monarch SSA Version 1.0 addition to habitat loss, we also explored other factors that may influence the current viability of the Tinian Monarch, including typhoons, drought, cattle ranching, and predation, among others. However, we found no evidence that these factors were having a measureable impact to individuals or the species as a whole. Executive Summary – Future Condition When assessing possible future conditions of the Tinian Monarch, we looked primarily to potential impacts from: 1) The introduction of a potential invasive predator, the brown treesnake (BTS), on Tinian – Based on our knowledge of impacts to Guam from the BTS, we believe its establishment on Tinian would likely result in the decimation or extirpation of the Tinian Monarch. Movement of civilian and military cargo and other materials that may contain BTS stowaways from Guam to the CNMI poses an enormous risk to Tinian and interdiction efforts are in place on both Guam and within the CMNI to prevent such a scenario. Despite improvements and advances in interdiction efforts, especially by the U.S. Navy, the risk of the invasive BTS remains high. 2) Future military activities on Tinian that may degrade or reduce forest habitat – The U.S. Navy has proposed future development activities, which may impact the Monarch according to their own assessment. Based on these plans, both the U.S. Navy and the Service assessed that approximately 11% of Tinian’s forest habitat will be lost, leading to approximately 8% of the Monarch population being permanently displaced (unable to reproduce) due to the reduction in the number of breeding territories (see Section 2.2.3 regarding about the Monarch’s territoriality). 3) Future civilian activities that may also degrade or reduce forest habitat through development – Based on rates of development in recent history and the CNMI’s stated interested in future developments on Tinian, we anticipate 4-6 development projects of a given size and involving the construction of permanent structures will occur over the next 16-66 years. Each project would cause the loss of approximately 2% of Tinian’s forest, leading to indefinite displacement (no reproduction) of approximately 1% of the Monarch population. 5 Tinian Monarch SSA Version 1.0 4) Military and civilian activities that increase the risk of wildfire – Based on our projections of future military and civilian activities, the risk of wildfire in the future varies from little or no increase to a substantial increase, depending on numerous specificities of the activities. We summarize these potential future impacts in five scenarios of the Tinian Monarch’s future condition. 6 Tinian Monarch SSA Version 1.0 Abbreviations and Acronyms 3Rs = Resiliency, Representation, and Redundancy ac = acres ADS = aerial bait delivery systems AAFB = Andersen Air Force Base BBS = Breeding Bird Survey BO = biological opinion BTS = Brown treesnake BTSWG = Brown Treesnake (Technical) Working Group CJMT = Commonwealth of the Northern Mariana Islands Joint Military Training cm = centimeters CNMI = Commonwealth of the Northern Mariana Islands DEIS = Draft Environmental Impact Statement DFW = Division of Fish and Wildlife Divert = United States Air Force Divert Activities and Exercises DLNR = Commonwealth of the Northern Mariana Islands Department of Lands and Natural Resources DOD = Department of Defense DOI = Department of the Interior EDRR = early detection and rapid response EIS = Environmental Impact Statement EMUA = Exclusive Military Use Area ESA = Endangered Species Act FDM = Farallon de Medinilla FEMA = Federal Emergency Management Agency FAA = Federal Aviation Administration ft = feet GISD = Global Invasive Species Database ha = hectares IUCN = International Union for Conservation of Nature in = inches km / km2 = kilometers / square kilometers LBA = Leaseback Area m = meters mi / mi2 = miles / square miles MITT = Mariana Islands Training and Testing Area MIRC = Mariana Islands Range Complex MLA = Military Lease Area NISC = National Invasive Species Council OIA – Office of Insular Affairs RBP = Regional Biosecurity Plan for Micronesia and Hawaii SE = Standard Error Service = United States Fish & Wildlife Service SSA = Species Status Assessment USAF = United States Air Force 7 Tinian Monarch SSA Version 1.0 U.S. Navy = United States Navy USDA-APHIS = United States Department of Agriculture Animal and Plant Health Inspection Services USFWS = United States Fish & Wildlife Service USGS = United States Geological Survey WWII = World War II (Second World War) 8 Tinian Monarch SSA Version 1.0 Table