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Bristle-thighed Curlews (Numenius tahitiensis) are large shorebirds that breed in Alaska and spend the nonbreeding season on atolls and small islands throughout Oceania. This life history pattern requires curlews to migrate long distances each year. In June 2007, we tagged 13 curlews with satellite transmitters at their southern breeding area in Alaska. We are using satellite telemetry to track these birds so we can map their migration routes and find the location of their nonbreeding areas. |
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A distinctive feature of the Bristle-thighed Curlew is its cinnamon-colored rump and tail. This feature helps distinguish curlews from similar species like the Whimbrel (N. phaeopus) particularly in places where the two species overlap in Alaska and Oceania. |
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In general, Whimbrels (like the one in this photo) are brown and grey in appearance in contrast to the brown and cinnamon tones of curlews. In addition, these two species can always be distinguished by their vocalizations. The curlew has a very distinct whistle, “chiu-eet”, which sounds like the whistle humans make when they are trying to get someone’s attention. |
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Bristle-thighed Curlew nest in two areas of Western Alaska, separated by about 300 km. The June 2007 field work occurred at the southern breeding area in the Andreafsky Wilderness of the Yukon Delta National Wildlife Refuge. |
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The June 2007 field crew. Left to right are: Bob Gill, Lee Tibbitts, Dan Mulcahy (veterinarian), Sathya Chinnadurai (veterinarian), Nathan Senner, Nils Warnock, Dan Ruthrauff, Sarah Warnock, and Stan Hermens (helicopter pilot). |
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Curlews breed in western Alaska in areas of low, tundra-covered hills. This is a view of Allen Creek in the western Andreafsky Wilderness. |
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Curlews nest and raise their broods in dwarf-shrub, lichen tundra. |
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Breeding birds also use tussock tundra which abounds with their preferred foods of insects and berries. |
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In most nesting areas such as the Andreafsky Wilderness, curlews generally nest on the lower slopes of hills near drainages, but their breeding territories generally encompass entire hillsides and tops of hills. |
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The plumage of curlews is very cryptic which allows the incubating birds to blend in with the surrounding tundra. Both males and females take turns incubating the 4-egg clutch. |
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Chicks hatch in late June and are almost immediately ready to leave the nest. The coloring and pattern of the downy chicks provides camouflage to protect them from avian and mammalian predators. Chicks follow their parents on long hikes to feeding areas. |
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Berries make up a large component of the diet of the curlews at all times of year. When birds arrive in Alaska in early May they eat berries that have been preserved over-winter in snow and by the time the chicks hatch in late June they feed on the year’s fresh crop. This photo shows crowberries (Empetrum nigrum), a ubiquitous plant on the Arctic tundra. |
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Another berry preferred by the curlews is the blueberry (Vaccinium uliginosum). |
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Insects, particularly mosquitoes, are abundant in western Alaska in summer and a preferred food of young curlew chicks. |
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Curlews are very attentive parents and fly close to intruders and alarm call to distract them from their young broods. We take advantage of this behavior by using a mist net to sweep birds out of the air when they approach us. |
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The captured birds are quickly removed from the mist nets and transported to camp via helicopter. The veterinarian is “standing by” at camp to perform the implant surgeries. |
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Once at camp birds are anesthetized while a small transmitter is inserted into the abdominal cavity. The surgical procedure takes less than 30 minutes. |
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Birds recover quickly and are ready for release within an hour of surgery. This photo shows a male curlew with a black leg flag inscribed “H8”. We use these conspicuous leg flags to identify individuals from a distance. |
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Birds fly upon release and return promptly to the task of tending their broods. |
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In the weeks following capture, we tracked the 13 birds as they moved short distances around the breeding area. In late July, we tracked the birds as they flew away from the breeding area and moved to staging sites on the Yukon-Kuskokwim Delta and Alaska Peninsula. The curlews will spend several weeks at the staging sites “fueling” for their upcoming flight. |
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The transmitters send frequent signals to orbiting satellites. Currently, the transmitters are turned on for 8 hours and then turned off for 24 hours. We download the raw data from the satellites and process the data on our computers using specific programs. The information we receive from the transmitters includes: location of the bird, body temperature, and battery charge. |
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As of 14 August, four curlews had left Alaska and were flying across the Pacific Ocean. Keep checking the web site to find out where their final destinations turn out to be! |
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Atolls, such as Tekakota in the Tuamotu Archipelago of French Polynesia are typical sites for curlews during the nonbreeding season. |
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Curlews use many terrestrial and marine habitats in Oceania. This photo of Reitoru Atoll in the Tuamotu Archipelago shows native forest, beach, and lagoon habitats. |
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On the northward migration, a curlew can go from it's tropical habitat to walking on snow in Alaska in 10 days. |
