Pacific Golden-Plovers Pluvialis fulva in American Samoa: Spring migration, fall return of marked birds, and other observations OSCAR W. JOHNSON', ROGER H. GOODWILL2, ANDREA E. BRUNER2, PATRICIA M. JOHNSON', ROGER S. GOLD2, RUTH B. UTZURRUM3 & JOSHUA 0. SEAMON3 'Department of Ecology, Montana State University, Bozeman, MT 59717, USA. owjohnson2105@aotcom 2Department of Biology, Brigham Young University-Hawaii, Laie, HI 96762, USA 3Wildlife Division, Department of Marine and Wildlife Resources American Samoa Government, Pago Pago, AS 96799, USA

Johnson, 0.W., Goodwill, R.H., Bruner, A.E., Johnson, P.M., Gold, R.S., Utzurrum, R.B. & Seamon, J.O. 2008. Pacific Golden-Plovers Pluvialis fulva in American Samoa: Spring migration, fall return of marked birds, and other observations. Wader Study Group Bull. 115(1): 20-23.

Keywords: Pacific Golden-Plover, Pluvialis fulva, radio-tagging, telemetry, spring migration, American Samoa, Oahu, Alaska, wintering ground fidelity, fall return rates, population estimates on Tutuila Island

In spring 2007, we radio-tagged and uniquely color-banded 30 Pacific Golden-Plovers Pluvialis fulva on wintering grounds at Tutuila Island, American Samoa (AS), and ten others on Oahu, Hawaiian Islands. All of these birds were territorial on short-grass (lawn) habitat. Spring migration from AS began during the second week of April well ahead of departure from Oahu which occurred in late April. The average at-capture body mass in both the AS and Oahu sample groups was statistically identical. Two of the birds were detected during subsequent monitoring surveys in Alaska. An AS plover was found on 25 April near the village of Egegik on the Alaska Peninsula, and a plover from Oahu was located on 23 May near Bethel in western Alaska. The route of the AS plover to Alaska is unknown, but from the great circle perspective a mid-Pacific flight traversing the Hawaiian Archipelago seems probable. A large percentage of the birds in both groups returned in the fall (AS 83%, Oahu 80%) and reoccupied previous territories. We estimated that the wintering population of Pacific Golden-Plovers on Tutuila Island was at least 500 birds. This was substantially greater than previous estimates.

INTRODUCTION METHODS

The winter range of Pacific Golden-Plovers Pluvialis fulva Over the period 28 March-5 April 2007, we captured with covers a vast area of the world (for maps see Byrkjedal & mist nets a total of 30 Pacific Golden-Plovers on Tutuila Thompson 1998, Johnson eta!. 2006, Hayman et a!. 1986). Island, the major landmass of American Samoa. All of the Prior to this investigation the only studies in which wintering birds were territorial individuals wintering on lawns at six plovers were either uniquely banded or banded and also radio- sites: Congregational Church (Kanana Fou Compound, tagged were conducted at Oahu, Johnston Atoll, and Saipan. n= 10), Catholic Church (Fatu-o-aiga Compound, n= 6), Vet- These studies revealed (see Johnson et al. 2006): that there erans Memorial Stadium (ri = 5), Leone High School (n= 5), is major migratory linkage between Oahu wintering grounds LINE Golf Course (n = 3), and Lion's Park (n = 1). The six and Alaska breeding grounds, that matted birds return at high sites are located in south-western Tutuila at approximately rates in the fall and have strong fidelity to specific winter 14°21 1S, 170°46'W. This part of the island is relatively flat territories, and that plovers wintering on Saipan most likely and contains an abundance of low grass habitat (lawns, golf nest in Siberia and migrate there via Japan. The islands of course, etc.) ideal for wintering plovers. The rest of Tutuila American Samoa are situated almost directly south of Alaska is mostly unsuitable for plovers as it is mountainous and at a distance of approximately 9,000 km (Fig. 1). From the forested. Our sample of birds consisted of 16 adult females, global (great circle) perspective, it seems likely that plovers 12 adult males, 1 first-year male and 1 first-year female. All wintering in American Samoa are linked to Alaska via the of the plovers captured on Tutuila were in advanced stages mid-Pacific Flyway. In an effort to demonstrate this connec- of pre-breeding molt. Thus, sexually dimorphic coloration tion, we banded and radio-tagged a sample group of birds on was obvious and the sexes were easily separable. For age Tutuila Island in spring 2007. The birds were captured only a and sex criteria in this species see Johnson & Johnson (1983) few days before they departed on northward migration. This and Johnson & Connors (1996). Methodology concerning investigation also provided an opportunity to estimate the color-banding, the attachment of transmitters, and the type number of plovers wintering on Tutuila relative to previous of transmitters used was identical to that described elsewhere counts by Beichle (2001), and to assess the site fidelity of by Johnson et at (2006). marked birds when they returned to the island in the fall. We monitored the radio-equipped birds at our banding sites

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Johnson of al.: Pacific Golden-plovers in American Samoa 21

Fig. 1. Arrow indicates the location of Tutuila Island in the Samoan Archipelago. Assuming a northward mid-Pacific migration route, the pathway would likely pass through the Hawaiian Islands. Various potential stopovers lie between Tutuila and Hawaii. Of these, we indicate the approximate locations of the Tokelau Islands (To), Phoenix Islands (Ph), Line Islands (U), and Johnston Island (Jo). with a hand-held receiver and also visually each day. During the night, we occasionally listened for signals at the island's airport (Tafuna International) where radio-tagged plovers often joined roosting aggregations. Monitoring continued until 12 April at which point we departed the island. We es- timated the wintering population of plovers on Tutuila from counts at our banding sites (collectively these made up a large fraction of plover habitat on the island) combined with nocturnal counts (using night-vision optics) at the airport. Large nighttime ag- gregations of plovers were present on taxi- ways and the ends of the runways at the airport, and it was apparent that these paved areas were the primary nocturnal roosting sites on Tutuila. Of our banding sites, the Ili'ili Golf Course held the largest num- ber of wintering birds. We censused the course systematically fairway by fairway (using an electric golf cart) six times from 1-12 April. The return of marked plovers at Tutuila in fall 2007 began in late August and peaked around mid-September. The final tally of returnees was made during the period 22-25 Oct. As an adjunct to the project on Tutuila and using the same methods, we banded and radio-tagged ten territorial plovers (eight adult males and two adult females) from a wintering ground counts at banding sites) occurred on 7 April. By 8 April, ten on Oahu. The birds were captured from 14-21 April 2007 at radio-tagged birds could no longer be found and the number Kualoa Park (21°30N, 157°50'W) on the northeastern coast of plovers at each banding site was reduced by about a half. of the island. Post-banding, OWJ and PMJ monitored these Similarly, nighttime counts at the airport dropped from 436 individuals until 27 April at which point all had migrated. plovers on 3 April to 236 on 10 April. The decline continued Their return in the fall was recorded by AEB who visited the and by the time our fieldwork ended on 12 April, 20 of the park several times in September and October. Altogether, 30 radio-tagged birds had disappeared. the wintering population at Kualoa Park consists of about Mean at-capture body mass of the Tutuila plovers was 70 plovers. 180 g (range = 122-212 g, n = 30), and there was essentially Monitoring of plover radio frequencies in Alaska was done no difference between the sexes (males = 180.3 g, n = 13; by cooperating biologists using fixed wing aircraft equipped females = 179.2 g, n = 17). We found no consistent relation- with VHF receiving antennae. The areas in which flights were ship between fat stores (as indicated by body mass at the time made, number of flights, and dates were as follows: Copper of capture) and the timing of migratory departure. Four of the River Delta, two flights, 28 April and 5 May; portions of the fattest birds (188-209 g) were still present on their territories region between King Salmon and Cape Seniavin, four flights, as of 12 April, while 20 others of varying weights (155-212 g) 23, 25, 29 April and 8 May; westward from Bethel, one flight, had already disappeared. At the completion of fieldwork on 12 23 May. The Copper River Delta is a major shorebird stop- April, mean at-capture body mass for both groups of plovers over outside the breeding range of Pacific Golden-Plovers. (the 20 birds that had departed and the ten still remaining at However, radio-tagged plovers have occasionally been found the study sites) was the same at 180 g. there in past studies (Johnson et at 2004). The other survey There were approximately 230 plovers resident at the regions were within the species' nesting range (Fig. 2). six banding sites, with the majority (at least 160) wintering on the Ili'ili Golf Course. Aside from the banding sites, we observed smaller numbers of plovers wherever there was suit- RESULTS able habitat—particularly along roadsides and on residential The first indications that plovers were leaving Tutuila on lawns. Considering all of the foregoing daytime observations spring migration (i.e., loss of several radio signals and lower together with nighttime airport counts, we estimated that the 22 Wader Study Group Bulletin 115 (1) 2008 Flg. 2. Gray shading represents the known breeding range of Pacific Golden-Plovers in Alaska (see Johnson et al. 2004, Savage & Johnson 2005). Open circles indicate locations of radio-tagged plovers. The bird near Egegik (Eg) was tagged on Tutuila; the bird near Bethel (Be) was from Oahu. Other abbreviations: Anchorage (Mc), Copper River Delta (CRD), Cape Seniavin (CS), ling Salmon (KS).

population of wintering plovers on Tutuila Island was at least 500 birds. Migratory departure of the radio-tagged plovers at Kualoa Park occurred during the period 24-27 April, about two weeks later than departures at Tutuila. Mean body mass of the Kualoa birds was 178 g (range = 158-202 g, n = 10), and there was no statistical difference between this weight and that of the Tutuila plovers (t = 0.30, P = 0.77, df = 38). The fat-free mass of fulva is about 105 g (Johnson et al. 1989), thus the birds weighed at both Tutuila and Kualoa contained a substantial quantity of pre-migratory fuel southern end of the species' breeding range, Fig. 2) has been (around 75 g on average) during the capture periods. Because 20 April over the past nine years (S. Savage, in litt). Such the birds in each sample group were captured several days timing suggests that these first arrivals might be plovers prior to migration, additional fattening probably occurred in from more distant wintering grounds to the south of Hawaii. all individuals before actual departure. Additional information concerning the chronology of spring Aerial monitoring in Alaska was hampered by unfavorable plover arrival on the Alaska Peninsula south of King Salmon weather and other problems. In the end, only a small part of is lacking, and in this regard it is noteworthy that the fulva the breeding range (perhaps 1-2%) was covered during the nesting grounds extending southward from King Salmon for survey flights. Two radio-tagged birds were found (Fig. 2): over 200 km (Fig. 2) were not discovered until 2004 (Savage a bird from Tutuila was located on 25 April about 8 km & Johnson 2005). southeast of Egegik (at approximately 58°09'N, 157°13'W) Great circle considerations suggest that the most likely on the Alaska Peninsula, and a Kualoa bird was detected migratory route between American Samoa and Alaska is along on 23 May about 65 km west of Bethel (at approximately a mid-Pacific pathway intersecting the Hawaiian Archipelago. 60°51'N, 162°57'W). The Tutuila plover (an adult male) This raises questions as to whether the northward passage of located near Egegik was radio-tagged on 28 March at the plovers involves a direct flight or stopovers en route. Of poten- Veterans Memorial Stadium, and weighed 189 g when cap- tial stopovers (Fig. 1), the Hawaiian Islands would probably tured. Post-tagging, we found this individual on his territory offer the most abundant resources. Spring aggregations occur each day until 11 April. He was not present on 12 April and in Hawaii, but it is uncertain if the plovers comprising these presumably had departed on migration. The Kualoa bird flocks are from local wintering grounds, transients from far- (also an adult male) weighed 169 g at capture on 19 April. ther south, or both. Though seemingly less plausible from the This bird disappeared from the study site on 27 April. Both great circle perspective, it is possible that a mid-Pacific path of the plovers detected in Alaska returned to their respective is not the primary route for plovers migrating front American wintering grounds in fall 2007. Samoa. Perhaps these birds travel westward through Micro- Fall return rates were essentially the same at both study nesia thence via inland Asia or Japan to nesting grounds in locations: Tutuila 83% (25 of 30 birds), Kualoa 80% (eight Siberia and/or Alaska (see Johnson et at 2006). Satisfactory of ten). All of the returnees reoccupied their previous win- resolution of these questions is unlikely until satellite tracking tering territories at the sites where they had been captured of plover-size shorebirds becomes possible. in the spring. Beichle (2001) counted Pacific Golden-Plovers in Ameri- can Samoa and neighboring Western Samoa at various times DISCUSSION from 1975 to 2000. From these counts, he estimated the number of birds wintering on each island in the archipelago. Migratory linkage between Hawaii and Alaska has been well Beichle's estimate for Tutuila was 200-300, considerably documented in recent years. Of 144 Pacific Golden-Plovers below our estimate of at least 500. We have no clear expla- radio-tagged from 1996-2005 at wintering grounds on Oahu, nation for this difference. Habitat expansion does not appear 38 were relocated in Alaska atter spring migration (Johnson to be a factor as it is unlikely that any significant increase et at 2004, OWJ unpublished records). The single Ameri- in the low grass cover preferred by plovers has occurred on can Samoa bird detected on the Alaska Peninsula indicates Tutuila during the interval between Beichle's estimate and similar linkage over a much greater distance. Spring depar- ours. Notably, the density of plovers wintering on the Ili' ili ture of plovers from Oahu typically occurs during the last Golf Course was impressively high at 3.02 birds/ha (160 week of April (Johnson & Connors 1996, OWJ unpublished plovers/53 ha) indicating an abundant prey base. This density records spanning the last quarter century) some two weeks falls at the upper end of the density range for plovers at 28 later than what we observed at Tutuila. The average date for Oahu golf courses (0.05-3.95 birds/ha) last censused during earliest spring sightings of fulva at King Salmon (toward the the 1991-92 wintering season (Johnson & Johnson 1993). Johnson et at: Pacific Golden-plovers in American Samoa 23

Concluding remarks King Salmon, Alaska. We are grateful to Susan Savage for arranging the survey flights southward from King Salmon. It is unfortunate that monitoring efforts in Alaska yielded only Dave Cox and Dominique Watts detected the plover radio- • one of the plovers radio-tagged on Tutuila. Nonetheless, this tagged on Tutuila during one of those surveys. Fred Broerman individual indicates that Alaska is a spring destination for at and Michael Rearden found the Kualoa plover near Bethel. least some of the plovers wintering in American Samoa. The We thank Mary Anne Bishop for aerial surveys at the Copper high return rate of plovers at Tutuila in the fall coupled with River Delta, Alaska. Brad Andres reviewed the manuscript their fidelity to wintering territories is identical to what occurs and made helpful suggestions. during autumn on Oahu. As in the main Hawaiian Islands, the choicest wintering habitat forfidva on Tutuila is man-made. REFERENCES Thus, we are in full agreement with Beichle's (2001) findings that plovers in the Samoan Islands have adapted well to urban Beichle, U. 2001. Pacific Golden Plovers Pluvialis fillva and other waders wintering grounds and to coexistence with humans. on the Samoan Islands: Wintering in a changing Polynesian landscape. Wader Study Group Bull. 96: 40-46. ByrkJedal, L & D. Thompson. 1998. Tundra plovers: The Eurasian, Pacific ACKNOWLEDGEMENTS and American Golden Plovers and Grey Plover. T & AD Poyser Ltd., London. We thank the people of Tutuila for kindly allowing us to cap- Hayman, P., J. Merchant & T. Prater. 1986. Shorebirds: An identification ture and monitor marked plovers on their lands. Fieldwork on guide to the waders of the world. Houghton Mifflin, Boston. the island was funded by Brigham Young University-Hawaii Johnson, O.W. & P.M. Johnson. 1983. Plumage—molt—age relationships in "over-summering" and migratory Lesser Golden-Plovers. Condor (BYU-H), and Federal Assistance in Wildlife Restoration 85: 406-419. Program (W-1-R-22) administered by the American Samoa Johnson, O.W. & P.M. Johnson. 1993. Counts of Pacific Golden-Plovers Department of Marine and Wildlife Resources (DMWR). (Pluvialis fulva) wintering on Oahu golf courses, 1992. Elepaio 53: Partial funding of travel to American Samoa was arranged by 39-43. Megan Laut through National Fish and Wildlife Foundation Johnson, O.W. & P.G. Connors. 1996. American Golden-Plover (Plinths Grant No. 2006-0181-008 administered by the Hawaii Divi- dominica), Pacific Golden-Plover (Pluvialis fulva). In: The Birds of North America No. 201-202. A. Poole and F Gill (eds). The Academy sion of Forestry and Wildlife. The Oahu portion of the study of Natural Sciences, Philadelphia, and The American Ornithologists' was supported by the Avian Influenza Program within the U.S. Union, Washington, D.C. Fish and Wildlife Service—Pacific Islands Office. DMWR Johnson, O.W., M.L. Morton, P.L. Bruiser & P.M. Johnson. 1989. Fat biologists Pulemagafa Siaifoi Fa'aumu, Ailao Tualaulelei, cyclicity, predicted migratory flight ranges, and features of wintering and Visa Vaivai assisted in mist netting and plover counts behavior in Pacific Golden-Plovers. Condor 91: 156-177. on Tutuila. Mr. Fa'aumu also provided invaluable liaison Johnson, O.W., C.D. Adler, LE. Ayres, M.A. Bishop, J.E. Doster, P.M. Johnson, R.J. Kienholz & S.E. Savage. 2004. Radio-tagged Pacific when arranging access to the various Tutuila study sites. Golden-Plovers: Further insight concerning the Hawaii—Alaska migratory The fieldwork at Tutuila involved several BYU-H students: link. Wilson Bull. 116: 158-162. Heather Dell, Katie LeFevre, and Luis Torrentera-Sanchez Johnson, O.W., R. Goodwill & P.M. Johnson. 2006. Wintering ground helped with netting, banding, and radio-tagging; Bridgette fidelity and other features of Pacific Golden-Plovers Pluviales fulva on Heiner and Annastasha Oloaga aided in locating marked Saipan, Mariana Islands, with comparative observations from Oahu, plovers during the fall surveys. A number of people assisted Hawaiian Islands. Wader Study Group Bull. 109: 67-72. in the capture of plovers at Kualoa Park on Oahu—we espe- Savage, S.E. & O.W. Johnson. 2005. Breeding range extensions for the Pacific Golden-Plover and Black-bellied Plover on theAlaska Peninsula. cially thank Joshua Fisher, Sam Goldstein, Shelly Kremer, Wader Study Group Bull. 108: 63-65. and Phillip Bruner. U.S. Fish and Wildlife Service biologists conducted the aerial monitoring in regions near Bethel and