ARTICLES ON HAWAIIAN
BIRDS AND BIRDWATCHING AND OTHER
PACIFIC WILDLIFE
The Bristle-thighed Curlew
The
Bristle-thighed Curlew (Numenius
tahitiensis) is a rare but annual migrant and winter visitor to the Hawaiian Islands,
with a few individuals, mostly young birds, over-summering in the Northwestern Hawaiian Islands. The bird was scientifically
named after its original discovery on the island of Tahiti in 1769. Its breeding grounds remained unknown until
1948 when the first nest was discovered. The species breeds locally on the Alaskan tundra and usually arrives in
the Hawaiian Islands by late August. In Hawai'i the species prefers undisturbed sandy shorelines and areas with
short grass or fields. Few locations in the Main Hawaiian Islands regularly hold individuals but one place where
one is almost guaranteed a sighting is the James Campbell National Wildlife Refuge on the northeast shore of O'ahu
at Kahuku. At this location a small flock of between ten and twenty birds regularly winter in the dunes and on
the grassy dykes between the refuge ponds. A few birds often over-summer here too. Bristle-thighed
Curlew photograph © Alan Tate.
Species Description
The Bristle-thighed Curlew is a large, mostly brown shorebird with a long decurved bill and a buffy-cinnamon rump. The tail is barred and the facial patterning recalls Whimbrel, with light and dark eye-stripes and supercilium. Superficially the species appear appears very similar to the Alaskan and Canadian races of Whimbrel, hudsonicus. At close range however the species can be seen to be darker and more contrasting above, with blackish-brown upperparts notched and spotted with rich cinnamon-buff, especially on the wing coverts. The species lacks barring on the undertail coverts and this is diagnostic of the species. The bristle-like feathers which are present at the base of the legs are often hard to see and visible only in good close views.
Distribution, Population and Habits
According to Rossair (1995) studies in the mid to late 1990's suggest that the total population of about 3,200 pairs is restricted to just two breeding areas, with 60% nesting in the southern Nulato hills on the Yukon delta, c.70 kilometres west of Anchorage, and the remaining 40% breeding in the central Seward peninsula. The latter site has been intensively studied by the Alaska Science Center (formerly the U.S. Fish and Wildlife Service) since 1988. According to Collar et al. (1994) the species population may be as high as 7,000 breeding birds and with a total population of 10,000. There is also the possibility that a small population breeds (at least intermittently) on the Chukotka peninsula in Russia. Bristle-thighed Curlews winter in Micronesia, Polynesia and atolls of the South Pacific, where they occur in a variety of habitats. According to Collar et al. (1994) the species can be found wintering on the Marshall Islands, Kiribati, Tuvalu, Tokelau (to New Zealand), Fiji, Tonga, Niue (to New Zealand), Western Samoa, American Samoa, Cook Islands (to New Zealand), Society Islands and Tuamotu archipelago (all French Polynesia), also reaching as far as the Kermadec Islands (New Zealand), Norfolk Island (to Australia) and the Pitcairn Islands (to U.K.).
Bristle-thighs are highly migratory and arrive on their breeding grounds during early May, where they draw attention to themselves with their aerial displays and diagnostic and far-carrying call - a hurried, rather curtailed "pee-uu-ee". The species often restricts its nesting to remote portions of the interior which are only accessible by small plane, although two sites along the Kougarok Highway out of Nome are well known and will usually provide sightings of the species, although hard uphill walking is apparently required. Due to the lack of natural predators in its wintering range Bristle-thighed Curlews have evolved a flightless wing moult which is unique amongst Shorebirds. Of course predators are now diverse and occur in many numbers on some of the species wintering islands and include cats, dogs, snakes, mongooses, rats and even humans. Throughout the Tuamotus it has been traditionally trapped for food, however following the decline of this subsistence hunting since the French government imposed sanctions on the possession and use of firearms, the greatest threat is from predators. On Rangiora Atoll the species' distribution is in inverse relation to that of humans and their commensal animals (Gill and Redmond 1992). On the breeding grounds the species is susceptible to predation by several bird species including Arctic Jaeger, Common Raven and several raptor species, as well as foxes. Humans also have an effect by off-road hunting of other species and activities associated with gold-mining, and in the future possibly by oil exploration.
Curlews eat a variety of food stuffs which consists of worms, grubs, beetles, invertebrates, crabs, maggots and especially on their wintering grounds, the eggs of nesting seabirds.
Bristle-thighed Curlews in Hawai'i
In Hawai'i the best areas for Bristle-thighed Curlew are mostly
in the Northwestern Hawaiian Islands, where there is no public access. Midway Atoll usually holds a few individuals
and they can often be seen on the short grassy areas, alongside the runways and along the sandy beaches (see Where
to Watch Birds in Hawai'i - Midway for access details). In the Main Islands, the areas most likely to produce sightings
are quiet, undisturbed beaches and coastal grassy fields and pastures.
Kaua'i:
The species has been seen on a few occasions at the airstrip just south of Hanapepe, near the saltponds. Here there is a large grassy area alongside the rocky coastline. The area is popular with visitors though, and so an early morning visit would be recommended. Polihale at the far western end of the island has produced the species on numerous occasions, and birds may be found anywhere along the beaches, in the dunes or the coastal grassland and scrub here. Along the north shore birds have been seen at Hanalei National Wildlife Refuge on a few occasions, although the habitat here is not really suited to the species. Kilauea Point National Wildlife Refuge is an unlikely site for the species but birds have been seen flying past the Point on several occasions, and have even stopped briefly along the cliff edges here. Birds are seen annually on the airfield at Lihue Airport by airport staff, but are seldom seen by visitors, and so although the habitat is ideal there is only a slim chance of seeing birds here. Nearby at Nawiliwili Lighthouse (Ninini Point) birds are sometimes seen flying past or overhead, and the odd bird may head for the airfield. Elsewhere on the Island birds are usually only seen flying past, presumably on their way to more favourable locations.
O'ahu:
The place to see the species in the Main Islands is James Campbell National Wildlife Refuge at Kahuku on the northeast coast. Here a regular flock of between ten and twenty birds over-winters and can be easily observed along the grassy dykes and in the coastal dunes. A few over-summer most years as well, although it is important to remember that the refuge is closed during the nesting season from February to August (see Where to Watch Birds in Hawaii - Oa'hu - James Campbell NWR for details). Elsewhere the species is hard to come by, but Ka'ena Point on the northwest tip of the island has had its fair share of records. An early morning visit to this site is recommended as it can get quite busy on certain days and later in the day the heat can become unbearable.
Maui:
Birds may be seen at Kealia Pond or in the adjacent dunes and beaches, but the species is highly irregular on this island, and any observer seeing one here should count themselves lucky. Kanaha Pond (near the airport) has also produced the species on the odd occasion.
Hawai'i:
South Point is the best location on the island to observe this species and at least a couple are recorded annually. Birds may also be seen along the coast here to the east and north, and birds are quite often seen on golf courses and hotel lawns in the area. Birds also sometimes show up at Aimakapa Pond, Kona, either on the beach, in the scrubby grassland or along the sandy shoreline of the pond itself.
Moloka'i:
On Moloka'i a small flock is said to be present year-round, although numbers are slightly
higher and sightings more reliable during the winter months. The BT Curlews hang out on the mudflats starting a
mile west of town makai of the Department of Hawaiian Homelands (they like to feed amongst the mangrove roots)
and at the Kapuaiwa Coconut Grove mud flats when there is a minus tide. Tide calendars can be purchased in town
at Fish & Dive. It is a small flock, 6 birds; three move to the shrimp farm in Palaau, but the owner of the
shrimp farm does not allow visitors. It is unknown where the other three go.
Occasionally the birds will move to the sewage treatment plant. They are sometimes seen, one to three, on the beach
in front of the 4 mile marker and on the rocky mud flat where Kawela Stream empties into the ocean just east of
the 5 mile marker.
References
COLLAR, N.J., M.J. CROSBY and A.J. STATTERSFIELD. 1994. Birds to Watch 2. The World list of Threatened Birds. Birdlife International. Cambridge , U.K.
DEL HOYO, J.; ELLIOTT, A.; and SARGATAL, J. 1992. The Handbook of the Birds of the World, Volume 3. Hoatzin to Auks. Lynx Edicions, Barcelona.
DIBBEN-YOUNG, A. 2003. Report to Birding HAwaii Website on birds present on Moloka'i.
HAYMAN, ., J. MARCHANT and T. PRATER. 1986. Shorebirds - An Identification Guide. Helm, Kent.
HAWAII AUDUBON SOCIETY. 1997. Hawaii's Birds. Hawai'i Audubon, Honolulu.
GILL, R.E., and R. L. REDMOND. 1992. Distribution, numbers, and habitat of Bristle-thighed Curlews (Numenius tahitiensis) on Rangiroa Atoll. Notornis 39: 17-26.
PRATT, H.D. , BRUNER, P.L. and BERRETT, D.G. et al. 1987. A Fieldguide to the Birds of Hawai'i and the Tropical Pacific. Princeton.
PRATT, H.D.. 1991. Enjoying Birds in Hawai'i - A Bird Finding Guide to the 50th State. Mutual Publishing, Honolulu.
ROSAIR, D. 1995. Bristle-thighed Curlew in focus. In Birding World volume 8, No. 8. Norfolk, U.K.
ROSAIR, D. and D. COTTRIDGE. 1995. Photographic Guide to the Waders of the World. Hamlyn, U.K.
Christian Melgar. Worthing, West Sussex, UK. 2002.
