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The Mariana Common Moorhen: Decline of an Island Endemic ’

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The Mariana Common Moorhen: Decline of an Island Endemic ’ The Condor93:3843 0 The Ccqer Ornithological Society 1991 THE MARIANA COMMON MOORHEN: DECLINE OF AN ISLAND ENDEMIC ’ DEREK W. STINSON Division of Fish and Wildlife, Saipan, MP 96950 USA MICHAEL W. &TTER Division of Aquatic and Wildlife Resources,P.O. Box 2950, Agana, Guam 96910 USA JAMES D. REICHEL Division of Fish and Wildlife, Saipan, MP 96950 USA Abstract. Current statusof Mariana Common Moorhens (Gallinula chloropusguami) in the Mariana Islands was determined by wetland surveys.A total of 300400 moorhensexist on Guam, Saipan and Tinian. Extinctions have occurred recently on Pagan and prehistor- ically on Rota. A review of literature, field notes, and habitat loss indicates the subspecies’ total population has probably been reduced by at least 36-52% in this century. The deg- radation and loss of wetlands and introduced competitors and predators pose the greatest threats to the moorhen in the Marianas. Kev words: Mariana Common Moorhen; Gallinula chloropusguami; Mariana Islands; stat& endangered. INTRODUCTION torical and present status of moorhens in the The Mariana Common Moorhen (Gallinula Marianas and outlines present threats and pros- chloropus guami), known locally as “Pulattat,” pects for their survival. is endemic to the Mariana Archipelago in the METHODS western Pacific. This moorhen resembles the Eurasian subspecies(chloropus, indica, and or- We surveyed moorhens on Guam, Saipan, Ti- ientalis) which have a frontal shield with a nian and Pagan (Fig. 1). These islands are of rounded top, but differs from these slightly in volcanic origin, but the surfacesof Saipan, Ti- coloration and/or size. G. c. guami differs from nian, Rota and northern Guam are primarily the Hawaiian endemic, G. c. sandvicensis, which limestone deposits that have been uplifted. has a larger, truncated frontal shield and is prob- To determine the historical populations of ably of New World origin (Hartert 1898, 1917; moorhens and the extent of habitat loss, we ex- Baker 195 1; Ripley 1977). The Mariana Com- amined accounts in the literature and examined mon Moorhen was historically found on the is- field notes of previous researchersin the Mari- lands of Guam, Saipan, Tinian, and Pagan (Ba- anas, including those from the Guam Division ker 195 1). Recent archaeological excavations of Aquatic and Wildlife Resources (DAWR) have found that it apparently was also once found and Commonwealth of the Northern Mariana on Rota (Becker and Butler 1988). The Mariana Islands Division of Fish and Wildlife (CNMI- Common Moorhen was listed as Endangered by DFW). DAWR undertook an island-wide wet- the U.S. Fish and Wildlife Service in 1984 land/moorhen distribution survey during 1988- (USFWS 1984). They identify habitat loss as the 1989. Most wetlands were surveyed twice: once most important factor affecting the Mariana during the wet seasonand again during the dry moorhen (USFWS 1988). The Mariana Com- season (generally, January or February through mon Moorhen shared wetland habitats with the June). Each wetland was identified as man-made Mariana Mallard (Anus oustaleti), now believed or natural, the vegetation identified and classified extinct (Engbring and Pratt 1985; Reichel and as dominant or subordinate, the percent open Lemke, in prep.). This paper summarizes the his- water approximated and any signs of moorhen recorded. Thirty to 60 min were spent at each wetland surveyed. Surveys at Fena Valley Res- I Received 19 March 1990. Final acceptance3 1 Au- ervoir were conducted by canoe. gust 1990. Current population estimatesare derived from [381 DECLINE OF MARIANA COMMON MOORHENS 39 wetland surveys. CNMI-DFW surveys involved visiting wetlands from several minutes to 6 hr W~OOE’ 146”bls and looking and listening. Wetlands were visited from one to 16 times between March 1989 and I May 1990 and most were visited both in the dry _18”oo ’ QPa!+* and rainy seasons.Surveys at Susupe Lake in- volved circumnavigation of the lake once on foot 0Alamagan I and four times with an inflatable boat. Moorhen 0 Guguan estimates for Susupe Lake and small wetlands are based on the highest number detectedduring I any visit. A planimeter was used in estimating o Sarigan wetland sizes and loss on Saipan. The lakes on I 0 Anatahan Pagan were visited during seven trips from 1983- 1990 which totaled 36 man-days. No moorhens - 16hlO ’ ’ Farallon de or permanent wetlands currently exist on any Medinilla other Mariana island. RESULTS AND DISCUSSION GUAM Quoy and Gaimard (1824-26, in Baker 195 1) first recorded the moorhen on Guam. Kittlitz (1858, in Hartert 1898) reported that moorhens were rare and inhabited “inaccessible reed-thick- ets.” The moorhen’s affinity for fresh and brack- ish water wetlands, fallow rice paddies, and cul- Guaml tivated taro patcheshas been noted by numerous Km authors (Hartert 1898, Seale 1901, Baker 1951, 0-0 Beaty 1967). During the early 1900s moorhens were an esteemedfood and hunting pressuremay FIGURE 1. Distribution of the Mariana Common have resulted in their relative rarity (Seale 190 1, Moorhen (* = islands with records of occurrence). Safford 1902, Bryan 1936). During the late 1940s moorhens were consideredcommon to abundant teen out of 18 wetlands (83%) used by moorhens on the island (Marshall 1949, Baker 195 1). Baker during the wet season were man-made as were (1951) found large numbers of birds along the 11 out of 14 (78%) used in the dry season.Wet- Ylig River and the Agana Swamp. In the 1970s lands used by moorhens were primarily vegetat- the population was estimated at from less than ed with nonpersistent emergents (Cyperaceae, 100 (Tenorio and Associates 1979) to 150 birds Gramineae, Panicum muticum). During this (Drahos 1977). Over the last 15 years, the moor- study, 15 out of 34 (43%) ofall wetlands surveyed hen population on Guam seems to have been and four out of 18 (22%) wetlands used by moor- relatively stable. Currently, the population is es- hens were ephemeral. The appearance of moor- timated to be loo-125 birds (DAWR unpubl. hens at newly flooded ephemeral wetlands in- data). dicates that intra-island movements between We found moorhens using 17 palustrine wet- ephemeraland persistentwetlands occurbut have lands and one lacustrine wetland on either a year- not been observed. round or seasonal basis (Table 1). With the ex- Fena Valley Reservoir, a deep, open water res- ception of Fena Valley Reservoir (8 1 ha) and the ervoir with steeply sloping sides, is a major dry reed-choked (Phragmites karka) Agana Swamp seasonrefuge for moorhens. Fringing vegetation (71 ha), the majority of wetlands inhabited by is limited to small isolated stands of emergents moorhens were lessthan 0.6 ha in size. Moorhens and some areas of the submergent Hydrilla ver- make extensive use of man-made wetlands in the ticillata. Our surveysindicate that moorhens pre- form of suburban ponding basins, golf course fer sites that support diverse emergent vegeta- ponds, and both large and small reservoirs. Fif- tion, contain both deep and shallow areas, and 40 D. W. STINSON, M. W. RITTER AND J. D. REICHEL TABLE 1. Size, location, estimated number of moorhens, and survey effort for Guam and Saipan wetlands. Est. no. surveyeffcnl Size Y%Y Wetland site Yz:- (ha) @a) Man br No. visits LocationUTM ’ Guam Barrigada pond 6 co.5 0.5 2 N 1490000 E26 1660 Prison pond 4 KO.5 Ki 0.5 2 N1487810 E260062 SGP upper 5 co.5 0:3 0.5 2 N1484375 E249630 SGI lower 3 0.5 0.5 0.5 2 N1404575E249000 SGI west 0.8 0.4 2 N1484625E249060 SGI diked fields : KO.5 0.3 :.: 2 N1484500 E249500 Fena Reservoir 32 81 77 6:0 2 N1478500E250181 Agana Swamp 8 71 18 1.0 N1489500E257250 Assupian pond 4 0.5 0.3 1.0 : N1472875E256750 Yabai wetland 4 1.0 2 N1469430 E256250 Navmag pond 4 t?: :::c 1.0 2 N1481930E248630 Navmag Swamp1 0:6 1.0 2 N1478560 E252560 Navmag Swamp2 ! 1.6 K 1.0 2 N1479000E252680 Pulantat west 4 1.2 0% 1.0 2 N1484580E254310 CCP #3d 4 co.5 2 N1479125E257625 Sarasapond 4 1.2 :8’ :.: 2 N1475000 E253180 Masso -Reservoir 4 1.6 1:2 1:o 2 N1488680E250180 Tumon Bay Pothole 4 0.2 1.0 2 N1495310E262300 Acapulco 8 ::; 0.4 1.0 1 N1475680 E255000 Saipan Susupe-Chalan-KanoaMarsh 20 185 3 4 2 N1673-1676650 E360-362100 SusupeLake 16 17 16 13 5 N1675300E361400 Tanapag 2 17 Oc 2 2 N1684100 E365500 Garapan 3 9 0.1 4 2 N1682200 E362600 Sadog Tase 10 10 7 14 N1683500 E364500 As Lito 5 2 &;a 1 1 N1672900E361900 Flares Pond 16 1 0-1C 13 13 N1674000E362920 Ragman North 16 1 0.5 8 16 N1678100 E367150 Ragman South 2 0.5 O-O.5 3 10 N1677160E367200 a UniversalTransverse Mercator coordinates. bShell Guam Inc. cSeasonally flooded only. 1 CountryClub of the Pacik, holeno. 3. have approximately equal portions of cover and War II but are no longer extensively cultivated. open water. Even though this type of habitat is The greater affluence and increasing population extremely limited at Fena, moorhen numbers of the island have put additional pressure on typically increase during the dry seasonand de- wetlands for development. Major portions of the crease during the wet season. Monthly counts Agana Swamp have been filled since the early varied from a high of 66 birds in June 1988 to 1970s and smaller wetlands have been converted a low of seven birds in March 1989 (DAWR to agricultural, commercial and residential uses. 1987-89). These data suggestthat moorhens im- migrate to the reservoir during the dry seasonas SAIPAN small ephemeral wetlands dry up and emigrate Oustalet (1896) was the first to report moorhens from the reservoir during the wet seasonas more on Saipan; he statesthat Marche collected six in wetlands become available.
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