Draft Post-Delisting Monitoring

Plan for the Tinian Monarch

(Monarcha takatsukasae)

U.S. Fish & Wildlife Service

Tinian Monarch at its nest

Photo courtesy of Tim Sutterfield, U.S. Navy
Recommended Citation:

U.S. Fish and Wildlife Service. 2004. Draft Post-delisting Monitoring Plan for the Titian Monarch Monarcha

takatsukasae. Endangered Species Division, Pacific Island Fish and Wildlife Office, Honolulu, HI. 19 pp.
Table of Contents 

Acknowledgments........................................................................................................................... ii 

Background......................................................................................................................................1 

Justification, Purpose, and Objectives.............................................................................................4 

Implementation ................................................................................................................................5 

Methods ...........................................................................................................................................7 

A. Monitoring the Tinian Monarch.....................................................................................7 

1. Roadside Point Count Surveys ............................................................................7 

2. Small-Scale Early Warning System Plots............................................................8 

3. Large-Scale Variable Circular Plot Survey .......................................................10 

4. Habitat Specific Demographic Study (not required) .........................................11 

B. Monitoring the Brown Treesnake ................................................................................12 

1. Monitoring .........................................................................................................12 

2. Interdiction Recommendations (not required)...................................................12 

C. Monitoring Land Use on Tinian...................................................................................13 

Reports, Analyses, and Listing Triggers........................................................................................14 

Literature Cited..............................................................................................................................16 

Tinian Monarch Draft Post-delisting Monitoring Plan i
Tinian Monarch Draft Post-delisting Monitoring Plan ii 

Acknowledgments

 This monitoring plan was developed by the U.S. Fish and Wildlife Service (Service) in 

cooperation with the U.S. Geological Survey Biological Resources Division, the U.S. 

Department of Agriculture Wildlife Services, the U.S. Navy, and the Commonwealth of the 

Northern Mariana Islands Division of Fish and Wildlife. Effective implementation of this postdelisting monitoring plan will be achieved only through the cooperation of these same partners. 

Dr. Eric VanderWerf, the Service’s Hawaiian Bird Recovery Coordinator, was the primary 

author. Assistance and valuable comments on drafts of this plan were provided by Fred Amidon, 

Jon Bart, Earl Campbell, Tina de Cruz, Holly Freifeld, Leila Gibson, Curt Kessler, Michael 

Lusk, Annie Marshall, Gad Perry, Gordon Rodda, Haldre Rogers, Derek Stinson, Tim 

Sutterfield, Scott Vogt, and Gary Wiles. 
Tinian Monarch Draft Post-delisting Monitoring Plan 1

Background

Tinian is a small [101 square kilometers (39 square miles)] island in the Commonwealth 

of the Northern Mariana Islands (CNMI), and is located three islands to the north of Guam. The 

human population of Tinian was estimated at 3,540 during a census in 2000. The majority of 

residents live in the island=s only town of San Jose at the southwestern edge of the island. The 

northern 71 percent of the island is leased to the U.S. Department of Defense (USDOD) for 

defense purposes. The remaining 29 percent of the island is divided between leased public 

property (67 percent), privately owned property (26 percent), and other public property (7 

percent) (Deborah Fleming, CNMI Division of Public Lands, pers. comm. 1999). 

Approximately 10 percent of the island is devoted to agriculture, while another 30 to 50 percent 

is used for cattle grazing (Engbring et al. 1986, Belt-Collins 1994). 

The Tinian monarch (Monarcha takatsukasae), or Chuchurican Tinian in Chamorro, was 

described by Takatsukasa and Yamashina (1931). It is a small [15 centimeter (6 inch)] forest 

bird in the monarch flycatcher family (Monarchidae), and has light rufous underparts, olivebrown upperparts, dark brown wings and tail, white wing bars, and a white rump and undertail 

coverts (Baker 1951). The monarch currently is found only on the island of Tinian, but 

examination of museum specimens by Peters (1996) suggested a now extirpated population may 

have occurred on the island of Saipan, just north of Tinian. The monarch also was reported from 

the tiny island of Aguiguan just south of Tinian in the early 1950s, but some authorities discount 

this report as an error (Engbring et al. 1986). 

Heavy disturbance of Tinian=s native forests began in the 18th century when the 

Spaniards used Tinian as a supply island for Guam and maintained large herds of cattle and other 

ungulates on the island (Fosberg 1960). In 1926, a Japanese company leased the entire island 

and cleared additional forested lands for sugarcane production (Belt-Collins 1994). During 

World War Two (WW II), the sugarcane plantations and most remaining native vegetation were 

destroyed by military campaigns and military construction (Baker 1946). After the war, the 

USDOD may have seeded the island with tangantangan (Leucaena leucocephala), a rapidly 

growing tree that is not native to the Marianas, to slow erosion (U.S. Fish and Wildlife Service 

[USFWS or Service] 1995, 1996). Currently, the vegetation on Tinian is highly disturbed, with 

tangantangan thickets being the most abundant habitat type (Fosberg 1960; Engbring et al. 1986; 

Falanruw et al. 1989). Engbring et al. (1986) estimated that 38 percent of Tinian was dominated 

by tangantangan, while Falanruw et al. (1989) estimated that 54 percent of the island was 

covered in secondary vegetation, which included tangantangan thickets. Only 5 to 7 percent of 

the island is estimated to support native forest, which is restricted to steep limestone escarpments 

(Engbring et al. 1986; Falanruw et al. 1989). 

The monarch inhabits a variety of forest types on Tinian, including native limestone 

forest dominated by figs (Ficus species [spp.]), Elaeocarpus joga, Mammea odorata, Guamia 

mariannae, Cynometra ramiflora, Aglaia mariannensis, Premna obtusifolia, Pisonia grandis, 

Ochrosia mariannensis, Neisosperma oppositifolia, Intsia bijuga, Melanolepis multiglandulosa, 

Eugenia spp., Pandanus spp., Artocarpus spp., and Hernandia spp., secondary vegetation 

consisting primarily of the non-natives Acacia confusa, Albizia lebbeck, Casuarina equisetifolia, 
Tinian Monarch Draft Post-delisting Monitoring Plan 2

Cocos nucifera, and Delonix regia, with some native species mixed in, and nearly pure stands of 

introduced tangantangan (Engbring et al. 1986; USFWS 1996). 

The Tinian monarch was listed as endangered in 1970 (35 FR 8491) under the authority 

of the Endangered Species Conservation Act of 1969 (16 U.S.C. 668cc). The monarch=s status 

remained as endangered under the Endangered Species Act of 1973, as amended (Act) (16 

U.S.C. 1531 et seq.). The decision to list the monarch as endangered was based on a report by 

Gleize (1945) of 40-50 monarchs on Tinian after WW II (52 FR 10890), but it is not clear if this 

report represented the number of birds seen, or an estimate of the total population on the entire 

island. Pratt et al. (1979) suggested that this estimate represented only the number of birds 

observed by Gleize in a specific part of the island. Downs (1946) reported that monarchs were 

restricted in distribution to distinct locations on the island, while Marshall (1949) considered the 

monarch to be abundant. Based on these reports it seems likely that monarchs were common in 

the small patches of remaining forest, but that their distribution must have been restricted and 

their population must have been small because so much of the forest had been destroyed. In the 

late 1970s, Pratt et al. (1979) estimated monarchs to number in the tens of thousands and to 

prefer tangantangan thickets. In May 1982, the Service conducted forest bird surveys of the 

Mariana islands using variable circular plot methods, during which the monarch was found to be 

the second most abundant bird species on Tinian, with a population estimated at 39,338 birds 

and distributed throughout the island in all forest types (Engbring et al. 1986). Engbring et al. 

(1986) recommended reassessment of the monarch=s endangered status, and on November 1, 

1985, the Service published in the Federal Register a proposed rule to delist the Tinian monarch 

(50 FR 45632). Based on comments received, the Service instead chose to downlist the 

monarch, and a final rule reclassifying the monarch from endangered to threatened was 

published in the Federal Register on April 6, 1987 (52 FR 10890). There is no recovery plan 

specifying delisting criteria for the Tinian monarch. 

A life history study of the Tinian monarch was conducted by the Service in 1994 and 

1995 (USFWS 1996). That study showed that monarchs forage and nest in native limestone 

forest, secondary forest, and tangantangan forest, but found some evidence indicating native 

limestone forest may be higher quality habitat for monarchs than secondary and tangantangan 

forests. Monarch home ranges were four to five times smaller in native limestone forest [1,221 

square meters (1,460 square yards)] than in secondary forest [5,126 square meters (5,608 square 

yards)] and tangantangan forests [6,385 square meters (7,636 square yards)], and population 

densities were higher in native limestone forest [30.7 birds per hectare (12.4 birds per acre)] than 

in secondary forest [7.7 birds per hectare (3.1 birds per acre)] or tangantangan forest [6.0 birds 

per hectare (2.4 birds per acre)]. Native tree species may have been preferred for nesting, and 

nesting success may have been higher in native limestone forest than in secondary and 

tangantangan forests, but additional information is required to confirm these patterns. Based on 

the results of that study, the island-wide monarch population was estimated to be approximately 

52,904 birds, and a recommendation was made to reassess the threatened status of the monarch 

(USFWS 1996). 

The Service conducted a second survey of the avifauna on Tinian in August and 

September 1996, using the same transects and methods as in 1982 (see Figure 1). The 1996 

survey estimated the monarch population at 55,721 birds (Lusk et al. 2000), which was 
significantly higher than the estimate of 39,338 birds found by Engbring et al. (1986). The 1996 

survey also found that vegetation density had increased significantly in all forest types since 

1982. Lusk et al. (2000) hypothesized that the increase in the monarch population was related to 

increases in density of vegetation in both native and introduced forest habitats, which may have 

been related to a decrease in grazing pressure. 

On February 3, 1997, we received a petition from the National Wilderness Institute to 

delist the Tinian monarch. We also received a similar petition dated December 6, 1997, from

Juan C. Tenorio & Associates, Inc. (Tenorio). As explained in our 1996 Petition Management 

Guidance (Service 1996), subsequent petitions are treated separately only when they are greater 

in scope or broaden the area of review of the first petition. The Tenorio petition provided no 

additional or new information than what was already provided in the NWI petition and will, 

therefore, be treated as a comment on the first petition received. On February 22, 1999, we 

published in the Federal Register a notice of petition finding and a proposed rule to remove the 

Tinian monarch from the Federal List of Endangered and Threatened Wildlife (64 FR 8533). We

received two letters of comment on the proposed delisting rule, one of which was from a 

scientific peer reviewer, and both supported the delisting of the Tinian monarch. On September 

21, 2004, we published a final rule removing the Tinian monarch from the Federal List of 

Endangered and Threatened Wildlife (69 FR 56367). That final rule was based on information 

from population surveys and demographic research, which indicated that the monarch has 

increased in number or is at least stable, that the primary listing factor, loss of habitat, has been 

ameliorated, and that the species is not currently threatened by any other factors. 

The future survival of the monarch is dependent on the availability of sufficient forest 

habitat. Monitoring of land use and forest clearing on Tinian therefore is necessary to help 

establish whether the monarch is threatened by the destruction, modification, or curtailment of 

its habitat or range. 

The brown treesnake is not known to be established on Tinian at this time and thus is not 

currently affecting the monarch, but establishment of the brown treesnake (Boiga irregularis) on 

Tinian would threaten the monarch and all other wildlife of Tinian. This nocturnal snake is 

native to northern Australia, New Guinea, and adjacent islands, and was accidently introduced to 

Guam in the late 1940s or early 1950s during military operations (Savidge 1987). The brown 

treesnake is a serious predator because it climbs exceptionally well and forages opportunistically 

on a wide variety of vertebrates, including birds and their eggs, reptiles, and mammals (Rodda et

al. 1999a). It has few competitors and no known predators in the Marianas, and can reach 

population densities of up to 80-120 snakes per hectare (32-48 snakes per acre) (Rodda et al. 

1999b). On Guam, predation by the brown treesnake decimated the avifauna, causing the local 

extirpation or complete extinction of 10 of the 13 native forest bird species on the island 

(Savidge 1987, Conry 1988, Rodda et al. 1999a). Declines in bird populations on Guam

occurred extremely rapidly once the brown treesnake became established (Savidge 1987, Wiles 

et al. 2003). 

There have been at least seven reports of snakes on Tinian from May 12, 1994, to 

November 9, 2003 (Hawley 2002, Haldre Rogers, USGS brown treesnake rapid response team, 

pers. comm. 2003). None of the snakes were captured to confirm identification, but several of 

Tinian Monarch Draft Post-delisting Monitoring Plan 3
the descriptions were consistent with brown treesnakes. Cargo shipments from Guam associated 

with development and resort construction, and the planned expansion of the Tinian airport, could 

accidentally introduce brown treesnakes to Tinian. The suspected establishment of an incipient 

brown treesnake population on Saipan provides another potential source from which snakes 

could reach Tinian (Hawley 2002). Effective interdiction programs are needed to reduce the 

chance of brown treesnakes reaching Tinian. If brown treesnakes reach Tinian, immediate action 

is required to prevent their establishment and the subsequent decline and possible extinction of 

the Tinian monarch in the wild. It is therefore vitally important to detect and eradicate any 

incipient populations of brown treesnakes before they become established on the island. 

Effective brown treesnake interdiction is crucial to the continued survival of the Tinian monarch, 

regardless of whether the monarch is listed. 

Justification, Purpose, and Objectives

Section 4(g)(1) of the Act, added in the 1988 reauthorization, requires the Service to 

implement a system, in cooperation with the States, to monitor for no fewer than 5 years the 

status of all species that have recovered and been removed from the List of Threatened and 

Endangered Wildlife and Plants (50 CFR 17.11, 17.12, 224.101, and 227.4). The purpose of this 

post-delisting monitoring (PDM) is to verify that a species delisted due to recovery remains 

secure from risk of extinction after it has been removed from the protections of the Act. The 

PDM fulfills the final process of species recovery. 

Section 4(g) of the Act explicitly requires cooperation with the States in development and 

implementation of PDM programs, but the Service remains responsible for compliance with 

section 4(g) and therefore must remain actively engaged in all phases of PDM. The Service also 

should seek active participation of other entities that are expected to assume responsibilities for 

the species= conservation post-delisting or have natural resources management mandates. 

In keeping with that mandate, the Service developed this draft PDM plan in cooperation 

with the CNMI Division of Fish and Wildlife (DFW), the U.S. Geological Survey Biological 

Resources Division (USGS-BRD), the U.S. Department of Agriculture Wildlife Services 

(USDA-WS), and the U.S. Navy. This plan has been reviewed by several independent scientific 

experts, including biostatisticians. A 30-day public comment period on this PDM plan was 

opened with the publication of a Notice of Availability in the Federal Register on December 13, 

2004. The Federal Register notice and the draft PDM plan also were posted on our Endangered 

Species Program=s national web page (http://endangered.fws.gov/) and the web page of the 

Pacific Islands Fish and Wildlife Office (http://pacificislands.fws.gov/). The final PDM plan and 

any future revisions also will be posted on these web pages. 

We intend to monitor the status of the Tinian monarch in cooperation with the CNMI 

DFW, the USGS-BRD, the USDA-WS, and the U.S. Navy, through regular field surveys of the 

distribution and abundance of the monarch, regular field surveys for brown treesnakes on Tinian, 

and tracking of land use and development on Tinian. If data from this monitoring effort or from

some other source indicate that the Tinian monarch is experiencing significant declines in 

abundance or distribution, that its survival or territory occupancy are declining significantly, or 

that it requires protective status under the Act for some other reason, the Service can initiate 

Tinian Monarch Draft Post-delisting Monitoring Plan 4
procedures to re-list the monarch, including, if appropriate, emergency listing. 

Implementation

Post-delisting monitoring is a cooperative effort between the Service, state, and foreign 

governments; other Federal agencies; and nongovernmental partners. Funding of post-delisting 

monitoring presents a challenge for all partners committed to ensuring the continued viability of

the Tinian monarch following removal of ESA protections. To the extent feasible, the Service 

intends to provide funding for post-delisting monitoring efforts through the annual 

appropriations process. Nonetheless, nothing in this Plan should be construed as a commitment 

or requirement that any Federal agency obligate or pay funds in contravention of the AntiDeficiency Act, 31 U.S.C. 1341, or any other law or regulation. 

The Pacific Region (Region 1) of the Service has the lead responsibility for this 

monitoring effort, but assistance from and collaboration with the U.S. Navy, the CNMI 

government, particularly the DFW, and the USGS-BRD are crucial for its successful 

implementation. In addition, assistance from the USDA-WS through contracts from other 

agencies will be an important component of monitoring of brown treesnakes on Tinian as part of 

this PDM plan, and for effective interdiction of brown treesnakes throughout the CNMI. There 

is no recovery team or recovery coordinator for the Tinian monarch; the Pacific Islands Fish and 

Wildlife Office (PIFWO) has responsibility within the Service for the Mariana islands, and 

biologists in the PIFWO therefore will take the lead in PDM plan implementation. 

The role of the PIFWO is to: 

$ produce a draft PDM plan for initial review; 

$ obtain peer review of the draft PDM plan from scientific experts and cooperators 

and incorporate their comments into the draft PDM Plan; 

$ write the notice of availability of the draft PDM plan for publication in the 

Federal Register; 

$ produce a press release for the draft PDM plan; 

$ distribute the draft PDM plan to interested parties through the Endangered 

Species Program and PIFWO web sites and by request; 

$ consider all comments on the draft PDM plan and produce the final PDM plan; 

$ distribute the final PDM plan to all cooperators; 

$ determine budget requirements to carry out the monitoring; 

$ coordinate variable circular plot surveys for the monarch along previously 

established transects on Tinian; 

$ coordinate mist-netting, banding, and monitoring of monarchs in early warning 

plots; 

$ track projects affecting land use on Tinian; 

$ compile all survey results and coordinate their analysis; 

$ ensure that survey methods prescribed in the PDM plan are followed; 

$ prepare interim and final reports for distribution to all cooperators and interested 

parties; 

$ coordinate any meetings or conference calls to discuss monitoring results and 

their interpretation. 

Tinian Monarch Draft Post-delisting Monitoring Plan 5
The role of the U.S. Navy is to: 

$ assist with conducting quarterly roadside point count surveys on Tinian; 

$ assist with relocating and clearing previously established transects on Tinian; 

$ assist with conducting Variable Circular Plot (VCP) surveys along previously 

established transects on Tinian; 

$ assist with mist-netting, banding, and monitoring of monarchs in the early 

warning plots; 

$ continue to provide adequate funding for brown treesnake interdiction measures 

associated with military training on Tinian. 

The role of the CNMI Division of Fish and Wildlife is to: 

$ assist with conducting semiannual roadside point count surveys on Tinian; 

$ assist with relocating and clearing previously established VCP transects on 

Tinian, as workload allows; 

$ assist with conducting VCP surveys along previously established transects on 

Tinian, as workload allows; 

$ assist with mist-netting, banding, and monitoring of monarchs in the small scale 

early warning plots, as workload allows; 

$ maintain snake traps at ports and quarantine yards on Tinian and support visual 

and dog team surveys; 

$ communicate with the PIFWO about any projects that will significantly reduce 

the amount of native limestone forest and other forest on Tinian. 

The role of the U.S. Geological Survey Biological Resources Division is to: 

$ assist with conducting VCP surveys along previously established transects on 

Tinian, as workload allows (Kilauea Field Station, Hawaii); 

$ assist with analysis of VCP survey data, including estimation of population size 

and trend (Kilauea Field Station, Hawaii); 

$ coordinate monthly surveys for brown treesnakes on Tinian and provide technical 

assistance for response to any reports of snakes on Tinian (Marianas-based staff 

of the Fort Collins Science Center); 

$ coordinate development and validation of a dog team trained to detect low density 

snake populations in forested areas. 

Tinian Monarch Draft Post-delisting Monitoring Plan 6
Methods

A. MONITORING THE TINIAN MONARCH 

Monitoring of the Tinian monarch will occur over a 5-year period from 2005-2010, and 

will be achieved through three complementary survey methods. First, roadside point counts 

based on the North American Breeding Bird Survey methodology will be used to monitor the 

abundance and distribution of monarchs across the island. Second, an Aearly warning system@

consisting of small scale study plots will be used to annually measure survival and territory 

occupancy of individually color-banded monarchs in areas where brown treesnakes might be 

most likely to occur, such as near the airport, commercial port, cargo off-loading and staging 

areas, and developments that are the ultimate destination of cargo received from other islands. 

Third, a large scale island-wide survey using variable circular plot will be conducted at the end 

of the 5- year monitoring period in 2010 to assess the species= overall status and to allow 

evaluation of long-term trends in population size and distribution through comparison with two 

previous variable circular plot surveys of the avifauna on Tinian (Engbring et al. 1986, Lusk et

al. 2000). 

In addition, this plan briefly describes the methods needed for a rigorous scientific study 

of habitat-specific demography of the Tinian monarch. Though not required to monitor the 

monarch=s status and recovery, habitat-specific demographic information about the monarch 

would allow more accurate assessment of the amount and distribution of different forest habitats 

needed for long-term persistence of monarch populations, and would allow more meaningful 

evaluation of how the species= survival might be affected by development and habitat loss in the 

future. A similar study was conducted previously (USFWS 1996), but the methods used in that 

study limit the interpretation of certain results, and additional information is needed to confirm

some patterns. 

1. Roadside Point Count Surveys 

The primary tool for monitoring the status of the Tinian monarch will be point 

count surveys using methods similar to those of the Breeding Bird Survey, which has 

been widely used to monitor status of bird populations in North America since 1966 

(Sauer et al. 2001). Similar surveys also have been used to monitor status of the 

endangered Mariana crow (Corvus kubaryi) on Rota (Plentovich et al. in prep.). To 

produce data that are comparable over time, the same route and the same stations should 

be used each year, and surveys should be conducted only during the first 5 hours after 

sunrise and only during favorable weather conditions (i.e., no more than light rain and 

wind not exceeding Beaufort scale 4). If possible, counts should be made simultaneously 

by two independent observers to allow assessment of inter-observer variation, and 

observers must be trained to recognize by sight and sound all species of birds present on 

Tinian. 

These surveys should be conducted at least biannually (twice a year), but 

quarterly surveys (four times per year) or even monthly surveys are preferable because 

they would provide more frequent assessment of the monarch population status and 

Tinian Monarch Draft Post-delisting Monitoring Plan 7
would help avoid potential biases caused by seasonal detectability and disruption of the 

normal monarch breeding cycle by typhoons. One survey should be conducted during 

the peak of the typical breeding season in May (USFWS 1996). If surveys are conducted 

quarterly, other surveys should occur at three-month intervals thereafter in August, 

November, and February. 

Breeding Bird Survey point counts usually are conducted along roads, but 

whether this is appropriate on Tinian will depend on whether sufficient roads are 

available that pass through forest habitat suitable for the monarch. The route should 

sample habitats that are representative of the entire island and that are likely to be 

accessible and to provide monarch habitat in the future. In North America, the standard 

length of Breeding Bird Survey routes is 24.5 miles, and this length should be used on 

Tinian if possible, but it may be shortened if insufficient roads are available. Trails may 

be substituted for roads, although this could require more time to complete surveys. 

Sampling stations should be located at 0.5-mile intervals along the route, so that a 24.5-

mile route would contain 50 stations. A 3-minute point count should be conducted at 

each station, during which all birds heard or seen within 0.25 mile of the station should 

be recorded. Changes in abundance over time should be assessed by using a t-test to 

compare the mean number of monarchs recorded per station each year at the same

season, with standard error having degrees of freedom equal to the number of stations 

minus one. This approach assumes that stations are random samples of monarch habitat 

on Tinian. 

2. Small-Scale Early Warning System Plots 

Small-scale monitoring of monarch populations in sensitive areas will serve as an 

early warning system that predation by brown treesnakes or some other factor may be 

threatening the monarch. This early warning system will involve identifying study plots 

near sites of potential brown treesnake introduction, mist-netting and color-banding adult 

monarchs in those plots, and then re-visiting the plots annually to measure adult survival 

and territory occupancy. Pacific island monarch flycatchers generally are nonmigratory, 

territorial year-round, and long-lived (Robertson et al. 1994, Sanders et al. 1995, 

VanderWerf 1998, 2004). A sensitive method of measuring short-term local trends in 

monarch populations is through the rate of turnover in territorial adults (VanderWerf and 

Smith 2002). In the Cook Islands, nest predation by rats (Rattus rattus) was identified as 

the primary threat to the Rarotonga monarch (Pomarea dimidiata) by measuring survival 

of banded birds (McCormack and Kunzle 1990, Robertson et al. 1994). In the Hawaiian 

Islands, elepaio (Chasiempis sandwichensis) populations that were experiencing high 

rates of adult mortality due to predation (VanderWerf and Smith 2002) and disease 

(VanderWerf 2001) were identified rapidly by the low survival of territorial adults and 

the high proportion of young birds in the breeding population. Passive survey methods 

like the variable circular plot and Breeding Bird Survey are less likely to detect initial 

population declines, especially if there are a large number of non-breeding Afloaters@ that 

fill the vacant territories left by birds that have been depredated. The method proposed 

here is more likely to quickly reveal early stages of brown treesnake predation or other 

Tinian Monarch Draft Post-delisting Monitoring Plan 8
threats and would provide valuable baseline data on the survival rate of Tinian monarchs 

under normal conditions when the population is stable or increasing. 

In order to provide an effective early-warning system for brown treesnake 

predation, plots must be placed strategically near areas most likely to receive brown 

treesnakes, such as the airport, commercial port, quarantine sites, cargo off-loading zones 

or staging areas, and sites that are the ultimate destination of materials brought from

other islands, like the appliance store that received cargo containing several snakes from

Guam in 1995. Due to the current manner in which sea and air cargo are transported and 

distributed on Tinian, it will be challenging to pinpoint sites where the risk is greatest. 

Creation of quarantine sites or cargo zones would greatly aid in the interdiction of brown 

treensnakes, and such sites could be used as foci for monitoring potential brown 

treesnake predation on Tinian monarchs. The number of early warning plots and their 

locations will depend on the number of sites identified by experts as most likely to 

receive brown treesnakes. 

The purpose of the early-warning monitoring system is to detect population 

declines at an early stage, so an objective was set of detecting an absolute decline in 

survival or territory occupancy of 20 percent or more per year. The sample sizes needed 

to detect such declines were determined by statistical power analyses. The ability of a 

statistical test to correctly distinguish between samples from two potentially different 

populations, such as survival rates before and after snake predation, is called the power of 

the test. In statistical terms, power is the probability of correctly rejecting the null 

hypothesis when it is false. The complement, erroneously accepting the null hypothesis 

when it is false, is called a type II error. In general, a decrease in the type II error rate 

results in an increase in the type I error rate (the probability of erroneously rejecting the 

null hypothesis when it is true), producing a trade-off between the two error rates (Sokal 

and Rohlf 1981, p. 168). In the case of the Tinian monarch, the consequences of making 

a type II error (accepting the null hypothesis of no decline when a decline actually is 

occurring) are more severe than the consequences of making a type I error (rejecting the 

null hypothesis of no decline when there really is no decline). Therefore, in designing 

the monitoring program a liberal approach was taken, and the desired power was set at 80 

percent, or a type II error rate of 20 percent. 

There are no data available on annual survival rates of the Tinian monarch, but in 

the Rarotonga monarch and the elepaio annual survival averages 80 percent and 81 

percent, respectively, in the absence of predation by alien species (Robertson et al. 1994, 

VanderWerf and Smith 2002, VanderWerf 2004). These related monarchs are 

behaviorally and ecologically similar to the Tinian monarch, so it is reasonable to use 80 

percent as an initial baseline estimate of annual survival for the Tinian monarch. Given 

the desired power of 80 percent, in order to detect a decline in survival or territory 

occupancy from 80 percent to 60 percent (a 20 percent absolute decline), a minimum of 

21 banded birds or territories is required each year (Sokal and Rohlf 1981, p. 766). 

Therefore, on the initial visit to each plot, at least 21 territories should be identified based 

on the presence of monarchs, and at least 21 adults within those territories should be 

mist-netted and banded with a unique combination of colored leg bands. In subsequent 

Tinian Monarch Draft Post-delisting Monitoring Plan 9
years, each territory should be revisited to determine whether it is still occupied and 

whether the banded birds are still present. Visits should occur from April through June, 

when monarchs usually are actively nesting and easiest to detect (USFWS 1996). If 

necessary, playbacks of recorded Tinian monarch vocalizations can be used to lure birds 

into a net for banding, and to locate birds more efficiently on subsequent visits to 

measure survival (Falls 1981, Johnson et al. 1981, VanderWerf et al. 2001). Some

natural mortality of banded birds is to be expected, and each year additional birds should 

be mist-netted and banded to restore the sample of banded birds to at least 21 individuals. 

 Estimates of survival and territory occupancy from subsequent years can be 

compared to the baseline estimate to determine if there has been a decline, which might 

be associated with predation by brown treesnakes or other factors. If there is no 

indication that survival or territory occupancy has declined from baseline conditions, then 

data from each year can be added to the baseline estimates. If, however, survival or 

territory occupancy shows a downward but statistically insignificant trend, then data from

each year should be kept separate and should not be pooled across years until it can be 

shown that the decline was temporary and values rebounded in subsequent years. For 

example, if the survival rates in the first and second years do not differ much (e.g., 80 

percent and 75 percent), then data from these years could be combined, thereby 

producing a larger baseline sample (n = 40) and providing for more powerful tests in the 

future. If, however, survival rates in the first two years differ by more than 5 percent, but 

are not significantly different, (e.g., 80 percent and 70 percent), then the data should be 

kept separate until the survival rate again approaches 80 percent, indicating the decline 

was temporary and probably due to factors other than brown treesnake predation, which 

presumably would result in a long-term reduction in survival. The accumulation of 

baseline data with each successive monitoring season will produce progressively larger 

sample sizes and greater statistical power to detect declines in survival in future years. 

Estimates of survival and territory occupancy should be calculated separately for each 

early warning plot and compared to the baseline individually because sites may be 

affected differently by predation and this information is needed to identify where 

incipient snake populations might exist. 

3. Large-Scale Variable Circular Plot Surveys 

At the end of the 5-year monitoring period in 2010, a single variable circular plot 

survey will be conducted to assess the species= overall status and to allow evaluation of 

long-term trends in population size and distribution through comparison with the two 

previous surveys of the avifauna on Tinian (Engbring et al. 1986, Lusk et al. 2000). To 

facilitate comparison of population estimates over time, surveys should use the same

variable circular plot methods and the same 10 transects and 216 stations used in 

previous surveys (Engbring et al. 1986, Lusk et al. 2000). These transects are located 2 

kilometers (1.24 miles) apart, with sampling stations at 150 meter (492 feet) intervals 

along each transect (Figure 1). Locations of all stations should be recorded using a 

Global Positioning System (GPS) unit so they can be overlaid on vegetation maps in 

order to calculate population density by habitat type. Surveys should be conducted 

during the first 5 hours after sunrise, and only during favorable weather conditions (i.e., 

Tinian Monarch Draft Post-delisting Monitoring Plan 10
no more than light rain and wind not exceeding Beaufort scale 4). At each station the 

distance from the observer to each individual of all bird species (not just monarchs) 

should be recorded for a period of 8 minutes, and the following additional information 

also should be recorded: starting time, cloud cover to nearest 10 percent, wind speed 

category on Beaufort scale, and vegetation density index in one of five categories (1 = 

complete forest canopy and dense understory with < 15 meter (49 feet) lateral visibility in 

all directions; 2 = complete or mostly complete forest canopy and 15-50 meter (49-164 

feet) lateral visibility in all directions; 3 = complete or mostly complete forest canopy and 

> 50-meter visibility in all directions; 4 = fragmented forest and > 50 meter (164 feet) 

visibility in < 50 percent of the surrounding area; and 5 = fragmented forest and >50 

meter (164 feet) visibility in > 50 percent of the surrounding area). Transects should be 

adequately cleared prior to surveys so that observers can move quickly and quietly along 

transects. This will help minimize disturbance and the effect of observers on the 

behavior of birds being surveyed and reduce violations of the assumptions of variable 

circular plot methodology. 

The timing of surveys differed in previous monitoring efforts (May in 1982, 

August-September in 1996), and a reviewer of the proposed delisting rule questioned 

whether the increase in number of monarchs reported from 1982 to 1996 could have been 

caused by the difference in timing of surveys. Detectability of birds often varies 

seasonally and with other factors, and can influence estimates of abundance (Freifeld et 

al. 2004). The timing of all future surveys should be consistent to avoid potentially 

confounding effects of season on detectability of birds and number of juveniles present. 

Reproduction varies substantially among years in two related species of monarch 

flycatchers, the Rarotonga monarch and the elepaio (Robertson et al. 1994, VanderWerf 

and Smith 2002, VanderWerf 2004), thereby producing short-term fluctuations in the 

number of non-breeding juveniles and subadults among years. It is therefore most 

appropriate to survey monarch populations early in the breeding season when adults are 

easiest to detect and the number of juveniles and subadult floaters is smallest. The peak 

in nest building by the Tinian monarch occurs in May (USFWS 1996), so May seems to 

be the most appropriate month for surveys. 

4. Habitat-Specific Demographic Study (recommended) 

This plan proposes to monitor changes in land use and forest extent on Tinian (see 

section C below) to help ascertain whether sufficient forest remains to support monarch 

populations, but it does not propose to investigate demography of the Tinian monarch in 

different forest types. However, habitat-specific demographic information about the 

monarch would allow better assessment of the amount and distribution of different forest 

habitats needed for long-term persistence of monarch populations, and would allow more 

meaningful evaluation of how the species= survival might be affected by development and 

loss of certain forest types or areas in the future. A rigorous scientific study of this type 

would require collection of the following data in native limestone forest, secondary 

forest, and tangantangan habitats: survival rates of adult males, adult females, and 

juveniles; rate of nest success and, more importantly, number of offspring produced each 

year per breeding pair; age at first reproduction; rates of dispersal into or out of each 

Tinian Monarch Draft Post-delisting Monitoring Plan 11
forest type, and accurate estimates of territory or home range size that are not biased by 

distribution of habitats or size of study plots. This information should be collected in 

each of at least two replicate plots in each forest type to avoid pseudoreplication. Some

of this information was collected in a previous study (USFWS 1996), but many of the 

results were affected by methodological limitations and additional data is required to 

confirm some of the patterns suggested by that study. 

B. MONITORING THE BROWN TREESNAKE 

For the purposes of this plan, there is an important distinction between monitoring of the 

brown treesnake and interdiction of the brown treesnake. Monitoring involves the periodic 

collection of data on the abundance of the brown treesnake in order to assess the threat of brown 

treesnake predation on the Tinian monarch. Interdiction involves measures designed to prevent 

the brown treesnake from reaching Tinian and becoming established on the island. Examples of 

interdiction measures include quarantine yards, cargo inspections, dog teams trained to detect 

snakes, and snake trapping. This post-delisting monitoring plan outlines a monitoring program

for brown treesnakes on Tinian, which presently does not exist, and, although interdiction of the 

brown treesnake is not strictly part of the monitoring plan for the Tinian monarch, this plan also 

makes recommendations for improving existing brown treesnake interdiction programs that are 

already in place in the CNMI and on Guam. Effective brown treesnake interdiction is crucial to 

the continued survival of the Tinian monarch, regardless of whether the monarch is provided 

protection under the Act. 

1. Monitoring 

The monitoring program for brown treesnakes on Tinian consists of two 

components: 1) a field crew trained on Guam to search for brown treesnakes on Tinian, 

composed of three technicians and one crew leader, who conduct standardized visual 

surveys for a total of at least 25 hours per month per person in different portions of the 

island, and who are on call for rapid response to any reports of snakes on Tinian; and 2) a 

one-half time dog team trained to detect snakes by smell in forested areas that have lowdensity snake populations. This monitoring program should be supported by a system of 

snake traps that are regularly maintained at strategic locations, such as the airport and 

quarantine yard at the commercial port. 

2. Interdiction (recommended) 

In addition to the monitoring described above, the following interdiction 

measures are important for preventing the brown treesnake from arriving on Tinian and 

becoming established, which would constitute a serious threat to the monarch: 

a) Construction of a brown treesnake barrier and quarantine yard at the 

commercial port on Tinian. In FY 2004, the Service provided funds ($200,000) for the 

construction of this barrier, similar in design to the recently completed barrier on Saipan, 

which is 3000 square meters (32,400 square feet) in size, has four-foot tall walls with a 

Tinian Monarch Draft Post-delisting Monitoring Plan 12
one-foot lip, and can accommodate up to 40 containers or break bulk cargo, with parking 

bumpers to protect the walls from damage (N. Hawley, pers. comm. 2004). 

b) Commitment from the U.S. Department of Defense for continued funding to 

support adequate brown treesnake interdiction associated with military training in the 

CNMI, which is contracted to the U.S. Department of Agriculture Wildlife Services. 

c) Continued support from the U.S. Office of Insular Affairs for base funding of 

brown treesnake interdiction at the commercial port and airport on Guam and in the 

CNMI; 

d) Financial support from the U.S. Department of Transportation and the CNMI 

government for adequate brown treesnake interdiction at the Tinian airport and on 

Saipan. 

C. MONITORING LAND USE ON TINIAN 

In addition to monitoring the monarch itself and the brown treesnake, monitoring land 

use on Tinian also is relevant to assessing the recovery of the Tinian monarch. The monarch 

originally was listed as endangered due to small population size and restricted distribution 

resulting from loss of forest habitat prior to and during WW II. Subsequent regeneration of 

forest habitat has allowed the monarch to recover, and monitoring the amount of forest on Tinian 

will help evaluate whether the monarch population may again be threatened by habitat loss. 

Several mechanisms already exist for tracking possible impacts of projects to the 

environment and natural resources on Tinian. Potential environmental impacts of major Federal 

projects must be reviewed under the National Environmental Policy Act (NEPA). 

Environmental Assessments and Environmental Impact Statements for such projects are 

reviewed by the Service. Impacts of Federal projects on the amount or quality of forest habitat 

available to the Tinian monarch thus can be tracked through these incoming documents. 

The Sikes Act Improvement Act of 1997 (Sikes Act) requires each military installation 

that includes land and water suitable for the conservation and management of natural resources 

to complete an Integrated Natural Resources Management Plan (INRMP), which integrates 

implementation of the military mission of the installation with stewardship of the natural 

resources found there. Each INRMP provides an assessment of the ecological needs on the 

installation, including needs to provide for the conservation of listed species, a statement of goals 

and priorities, a detailed description of management actions to provide for these ecological 

needs, and a monitoring and adaptive management plan. The military develops each INRMP in 

collaboration with the Service, and with State, territorial, or commonwealth resource 

management agencies. 

The INRMP for military training in the Marianas includes several projects designed to 

increase the amount of forest on Tinian and that will enhance and monitor habitat suitable for the 

Tinian monarch (USDOD 2003, p. 106). These projects include: 1) reforestation on military 

leased lands using native tree species; 2) planting of native forest understory species to improve 

Tinian Monarch Draft Post-delisting Monitoring Plan 13
habitat for threatened and endangered species and enhance biodiversity; 3) a vegetation survey 

that will map, describe, and verify in the field the vegetation communities on military leased 

lands; and 4) establishment of long-term natural resource monitoring plots on military leased 

lands. 

Non-Federal projects, such as those undertaken by Commonwealth or local governments, 

do not require review under NEPA, and their potential impacts may be more difficult to track. In 

these cases assistance from biologists with the CNMI and the U.S. Navy who visit Tinian more 

frequently and are familiar with local conditions will be necessary in order to effectively gather 

adequate information on potential impacts to forest habitats. 

Previous surveys of the avifauna on Tinian estimated forest density at each sampling 

station (Engbring et al. 1986, Lusk et al. 2000). This information proved to be a valuable tool 

for monitoring extent and density of forest habitat, and the delisting rule was based in part on 

information gathered during these surveys, which showed an increase in forest density since 

WW II. Future surveys on Tinian, including the variable circular plot survey in 2010 and the 

more frequent point count surveys, should continue to collect information about extent and 

density of forest cover. 

Reports, Analyses, and Listing Triggers

Annual reports summarizing the activities, data collected, and results of each component 

of the PDM plan should be submitted by cooperators to the PIFWO. These reports must be 

prepared and reviewed in a timely manner to ensure that adequate data are being collected, to 

allow evaluation of the efficacy of the monitoring programs and their modification if necessary, 

and to allow periodic assessment of the status of the monarch. The PIFWO will compile all 

results and, after discussion with cooperators if necessary, synthesize an overall report that will 

be distributed to all cooperators. Each annual report will comment on the status of the monarch 

relative to the need for relisting. 

Declines in bird populations on Guam due to predation by the brown treesnake occurred 

very rapidly (Wiles et al. 2003). If monitoring reveals that brown treesnakes are reproducing on 

Tinian or that the frequency and/or distribution of brown treesnake reports are increasing to an 

extent that the snake appears to be established on Tinian, such evidence would constitute new 

information that the monarch is in danger of extinction due to predation, and would trigger 

commencement of listing procedures, possibly including emergency listing if appropriate. 

If results from any of the three methods of monitoring the monarch (point counts, early 

warning plots, and the Variable circular plot survey) indicate that a decline may have occurred, 

then the cooperators will review all available monitoring data, evaluate possible causes of the 

apparent decline, and determine the most appropriate response. The monarch population could 

decline for a number of reasons other than loss of habitat or predation by brown treesnakes, and 

it will be important to consider the effects of potentially confounding factors, such as poor 

weather conditions during surveys, disruption of typical monarch breeding phenology by unusual 

climatic events, and short-term reductions in monarch survival or population size associated with 

typhoons or local disturbance. Results of the variable circular plot survey conducted in 2010 

Tinian Monarch Draft Post-delisting Monitoring Plan 14
will be compared to results of previous variable circular plot surveys, which estimated the 

monarch population to be 39,338 birds in May 1982 (Engbring et al. 1986) and 55,721 birds in 

August-September 1996 (Lusk et al. 2000). If the population estimate from the 2010 survey is 

significantly lower than 39,338 or 55,721 birds at the same season, suggesting a decline, and 

results are not confounded by the factors listed above, then the data should be examined transect 

by transect to determine where the decline occurred and what may have caused it. Likewise, if 

results of point counts indicate that abundance has declined significantly or the results of early 

warning plots indicate survival or territory occupancy has declined, then the data should be 

examined geographically to determine where decline(s) occurred. Any areas identified in this 

way should be targeted for more intensive brown treesnake visual surveys and trapping and for 

more intensive investigation of monarch demography to determine the cause of decline. If a 

significant decline in relative abundance or survival persists for 2 consecutive years, then 

relisting the monarch may be warranted, even if the establishment of brown treesnakes has not 

been confirmed. 

Large scale loss of forest habitat also could require that steps be taken to ensure the longterm survival of the monarch. If results of land use tracking indicate that the range of the 

monarch is declining due to loss of forest habitat, then actions should be taken to ensure that 

continued habitat loss does not threaten the monarch with extinction. Such actions include, but 

are not limited to: candidate conservation agreements; conservation easements; habitat 

enhancement in alternative areas; and expansion of the 379 hectares (936 acres) A1994 leaseback 

land@ set aside south of the Exclusive Military Use Area as a conservation area for the protection 

of endangered and threatened wildlife, particularly the Tinian monarch (Tenorio and Associates 

1998; USA and CNMI 1999). 

At the end of the 5-year monitoring period in 2010, a final report summarizing the results 

of the monitoring effort will be prepared, the availability of which will be published in the 

Federal Register. The final report should be suitable for publication in a peer-reviewed 

scientific journal, and will include a discussion of whether monitoring should continue beyond 

the 5-year period for any reason. If the results are inconclusive, monitoring should continue and 

the monitoring plan should be modified as appropriate. If there is no indication that the monarch 

population has declined during the 5-year monitoring period, no reason to believe that it will 

decline in the foreseeable future, and no reason to believe that the chance of brown treesnake 

introduction will increase in the foreseeable future, then monitoring can be discontinued at that 

time. However, predation by brown treesnakes will remain a potential threat to the Tinian 

monarch until the possibility that snakes are introduced to Tinian has been removed, and brown 

treensnake interdiction measures, therefore, must continue until that time.

Tinian Monarch Draft Post-delisting Monitoring Plan 15
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Tinian Monarch Draft Post-delisting Monitoring Plan 19