Micronesica 38(2):221–237, 2006 Observations on the birds of Kwajalein Atoll, including six new species records for the Marshall Islands ERIC A. VANDERWERF U.S. Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office, 300 Ala Moana Blvd, Room 3-122, Box 50088, Honolulu, HI 96850 Abstract—Kwajalein is the largest atoll in the world and is located in the western chain of the Marshall Islands. As part of a team of biologists from the U.S. Fish and Wildlife Service, I conducted bird surveys from 7–20 October 2004 on seven islets in Kwajalein Atoll that are leased by the U.S. Army. This proved to be exceptionally rich period for migratory birds on Kwajalein. I observed a total of 36 bird species, including 6 species not previously recorded in the Marshall Islands (Common Ringed Plover Charadrius hiaticula, Semipalmated Plover Charadrius semipalmatus, Common Greenshank Tringa nebularia, Red Knot Calidris canutus, Long-Billed Dowitcher Limnodromus scolopaceus, and Common Snipe Gallinago gallinago) and 4 species recorded only once before (Marsh Sandpiper Tringa stagnatilis, Red-necked Stint Calidris ruficollis, Curlew Sandpiper Calidris ferruginea, and White- winged Tern Chlidonias leucopterus). Many of the observations were documented with photographs. The water catchments, irrigated and fer- tilized lawns, and open fields on Kwajalein Atoll may attract migratory birds, or at least cause them to linger, making their detection more likely. Only 4 seabird species were documented or suspected to breed on the islets surveyed. Eradication of alien predators would greatly enhance the suitability of Army-leased islets as nesting sites for seabirds. Introduction Kwajalein is the largest atoll in the world and is located in the western chain of the Marshall Islands (8° 44' N, 167° 44' E). It comprises 97 small islets around a central lagoon that is up to 120 km across. Politically, Kwajalein is part of the Republic of the Marshall Islands, but 11 islets in the Atoll are wholly or partially leased by the U.S. Army. The avifauna of Kwajalein Atoll has been relatively well documented compared to most parts of Micronesia and other Pacific Islands, thanks largely to the efforts of Schipper and Clapp beginning in the late 1970s (Schipper 1985, Clapp 1990, Clapp & Schipper 1990). Avifaunal surveys of the islets leased by the U.S. Army were initially conducted by Clapp (1990) as part of an Environmental Assessment of military activities at Kwajalein Atoll. The U.S. Fish and Wildlife Service (USFWS) has conducted similar surveys at Kwajalein 222 Micronesica 38(2), 2006 every other year since 1994 and has made recommendations to the Army for min- imizing impacts and managing marine and terrestrial natural resources. In October 2004, I participated in a portion of the terrestrial surveys for the USFWS. This period proved to be exceptionally rich in migratory birds on Kwajalein. Here I report on new and noteworthy bird observations made during and incidental to those surveys. Methods As part of a USFWS team of biologists, I helped conduct terrestrial surveys at Kwajalein Atoll from 7–20 October 2004. Most of our time was spent on Kwajalein and Roi-Namur, the two largest islets in the atoll, but nine other islets leased by the U.S. Army were also surveyed (Fig. 1). I participated in surveys on Gagan, Omelek, Ennugarret, Enewetak, and Gellinam, and additional surveys were conducted on Meck, Ennylabegan, Legan, and Illeginni from 11–19 November 2004 by Naomi Bentivoglio and Patrice Ashfield. Surveys of shoreline areas were conducted by walking the perimeter of each islet to count birds in shoreline and exposed reef habitats. Surveys coincided with low tides to maximize exposed reef habitat. The interior of smaller islets (those other than Kwajalein and Roi-Namur) also were surveyed entirely on foot. The interior of Ennugarret and Enewetak, which are covered with dense native littoral forest dominated by Pisonia grandis, Guettarda speciosa, Pandanus tectorius, Cordia subcordata, and Neisosperma oppositifolium (Whistler and Steele 1999), were surveyed by walking parallel transects throughout the forest. On Kwajalein and Roi-Namur, the two largest and most developed islets, interior areas were sur- veyed on foot, bicycle, and by golfcart from existing roadways. The developed areas in the interior of Kwajalein and Roi-Namur were surveyed multiple times, and the number of birds observed was averaged for the more common species. Information on breeding status was recorded for each species. The effect of tide on the number and diversity of birds at the water catchment on Roi-Namur was investigated by conducting repeated surveys at different times and under different tidal conditions. Tide heights and times were obtained from the website <www.mobilegeographics.com:81/locations/3203.html>. Results I observed a total of 36 bird species during surveys at Kwajalein Atoll in October 2004, including 6 species previously unrecorded in the Marshall Islands (Common Ringed Plover Charadrius hiaticula, Semipalmated Plover Charadrius semipalmatus, Common Greenshank Tringa nebularia, Red Knot Calidris canutus, Long-Billed Dowitcher Limnodromus scolopaceus, and Common Snipe Gallinago gallinago) and 4 species recorded only once before (Marsh Sandpiper Tringa stagnatilis, Red-necked Stint Calidris ruficollis, Curlew Sandpiper Calidris ferruginea, and White-winged Tern Chlidonias leucopterus). The occur- VanderWerf: Birds on Kwajalein 223 Figure 1. Map of Kwajalein Atoll, showing islets surveyed by the USFWS in 2004. rence of many of these species was documented with photographs, some of which are included below. Details of these records and other noteworthy observations are given in the species accounts below. Nomenclature follows Wiles (2005). Other species observed during these surveys, but for which I have no noteworthy information, included Wedge-tailed Shearwater (Puffinus pacificus), Brown Booby (Sula leucogaster), Red-footed Booby (Sula sula), Great Frigatebird (Fregata minor), and Great Crested Tern (Sterna bergii). SPECIES ACCOUNTS Sooty or Short-tailed Shearwater (Puffinus griseus or P. tenuirostris). I observed five dark shearwaters flying southeast along the northern end of Roi- Namur during 30 minutes of observation on 9 October. On 18 October, I observed 52 dark shearwaters flying southeast along the southern side of Kwajalein during 65 minutes of observation. All birds were outside the barrier reef and were too far away to allow identification as Sooty or Short-tailed, but they could be distin- guished by shape and color from Wedge-tailed Shearwaters (Puffinus pacificus), which were also flying past. No shearwaters were observed feeding and all appeared to be transiting the area. Hundreds of Short-tailed Shearwaters have been observed in May near Guam and Chuuk (Wiles et al. 2000) in western Micronesia, and it has been suggested that similar numbers may pass through 224 Micronesica 38(2), 2006 eastern and central Micronesia (Skira 1991). Short-tailed Shearwaters breed in southeastern Australia from September-April, and Sooty Shearwaters breed mainly on islands off New Zealand, Tasmania, and Chile in September-May. After breeding, both species are thought to embark on a clockwise migration around the Pacific, but the route taken by most birds is not well documented. Pacific Reef-Heron (Egretta sacra). This species is a common resident on Kwajalein Atoll and throughout the Marshall Islands (Amerson 1969, Clapp 1990). In 2004, we observed small numbers on all islets surveyed, with the most birds on Roi-Namur (24) and Kwajalein (12), and a few on the nine smaller islets (1–6 each, 27 total). The pied color morph was most numerous (41%), followed by gray (38%), and white (21%). Clapp (1990) reported fewer total birds (26), but similar proportions of color morphs (42% pied, 27% gray, and 31% white). Northern Pintail (Anas acuta). The Northern Pintail is an uncommon but regular migrant in the Marshall Islands, and is the most frequently observed waterfowl species in the region (Amerson 1969, Clapp 1990, Udvardy and Engilis 2001). I observed up to six pintails on Kwajalein on 18 October 2004. Birds were seen in a puddle at the west end of the runway and flying around open areas near the runway. A flock of six waterfowl observed flying offshore 1 km south of Kwajalein on 18 October may also have been pintails, but they were too distant to identify with certainty. Pacific Golden-Plover (Pluvialis fulva). This species is a common migrant in much of the Pacific, including the Marshall Islands (Amerson 1969, Clapp 1990). On Kwajalein Atoll it was abundant, and was the second most numerous bird species on most islets surveyed, after Ruddy Turnstone. The largest numbers were observed on Kwajalein (470) and Roi-Namur (278), with fewer birds on the nine smaller islets (7-39 each, 160 total). The number on Roi-Namur is similar to previous counts of 200 by Amerson (1969), 222 by Schipper (in Clapp 1990), and 230 by Clapp (1990). The total for Kwajalein is higher than a previous count of 180 by Clapp (1990). On Roi-Namur, many plovers roosted in the water catch- ment at high tide, when virtually all shoreline habitat was inundated. On Kwajalein, few plovers used the water catchment area, and most were dispersed over large grassy areas. On Roi-Namur and smaller islets, which were surveyed entirely, the number of plovers reported probably is an accurate census. Surveying all parts of Kwajalein Islet was not possible, so the number of birds reported is lower than the actual number present, but can be used as an index of abundance to monitor plover populations over time if the survey route remains consistent. Lesser Sand-Plover (Charadrius mongolus). At least two Lesser Sand- Plovers were present on Roi-Namur on 8 and 10–12 October. A single bird was first observed foraging on exposed reef flat at low tide on the northeastern side of Roi-Namur on 8 October (Figure 2a).