January 23, 2007
Shorebirds complete marathon trans-Pacific flights - Search launched for missing trans-Pacific godwits and curlews
- Bob Gill: United States Geological Survey Alaska Science Center.
Buoyed by the success we had in 2005 in attaching satellite transmitters to nesting Bar-tailed Godwits (see January 2006 Tattler), we expanded the effort in 2006 to include both Bar-tailed Godwits and Bristle-thighed Curlews. Between early August and late September we followed the southward flights of 9 Bristle-thighed Curlews and 5 Bar-tailed Godwits as they departed their Yukon-Kuskokwim Delta staging grounds.
Bar-tailed Godwit in flight. © 2006 Available Light Images. Press image for enlargement.
Amazingly, all of the curlews were tracked to French Polynesia and the southern Line Islands. Bar-tailed Godwits were likewise followed across the Pacific along almost their entire flight, but continuing problems with battery failure prevented us from tracking birds to their final destination in either New Zealand or eastern Australia. For example, one godwit got within 1,500 km of New Zealand when its battery died. At the time it was well past Fiji and flying strongly at over 80 km/h. Another godwit was 2,500 km from Queensland and flying steadily at 50 km/h when its battery failed. Yet a third godwit had its battery die before it even departed on migration. Another bird spent 9.5 days!! in the air before it landed on an atoll east of New Caledonia. It got caught up in some pretty strong headwinds north of Hawaii and again past Fiji. The latter caused the bird to abruptly head west where it stopped on New Caledonia.
This sub species of Bar-tailed Godwits that nest in Alaska must complete the longest known single flight for a land bird, 11,000 km, to Australia and New Zealand.
Among the Bristle-thighed Curlews, two birds reached French Polynesia but their transmitters stopped reporting before they settled on a specific non-breeding area. Both were within 1,000 km of the nearest atoll known to host Bristle-thighed Curlews when their transmitters last reported. Since the transmitters were on a 48-h reporting cycle birds easily could have reached land during the following two days and shed their transmitters before the next reporting cycle. [It is beyond the scope of this article to present other details of the study. These you’ll see shortly in the Tattler and other scientific journals.]
Bristle-thighed Curlew on Sth Tuamotu Islands. © 2006 Phil Hansboro. Press image for enlargement.
In the mean time, anyone with an interest in Bar-tailed Godwits and Bristle-thighed Curlews can provide invaluable help by observing one or more of the marked godwits and curlews whose radios stopped prematurely. Each bird carries a black flag inscribed with a two-digit alphanumeric code and an antenna should be clearly visible extending from the bird’s lower back or from under its tail. For godwits in particular, observing one of the birds in question will demonstrate that it did indeed complete its migration (Bar-tailed Godwits with transmitters and engraved flags were observed in Australia and New Zealand last year).
Please send information directly to David Melville, Adrian Riegen, Phil Battley, or myself. Besides being profusely acknowledged in our writings about the birds, you will become an honorary member of the Alaska Shorebird Group and receive a handsome hat and patch.
Now to track the Godwits on their northward migration
Although the baueri sub-species of Bar-tailed Godwit fly directly across the Pacific on their southern migration it is likely that these birds fly north via the Yellow Sea to their breeding grounds. How they then fly to Alaska is unknown.
In early February 2007 a team of U.S. biologist will travel to New Zealand to work with colleagues in applying satellite transmitters to Bar-tailed Godwits. Bob Gill and veterinarian Dan Mulcahy of the U.S. Geological Survey in Alaska and Nils Warnock of PRBO Conservation Science in California with work with Phil Battley, David Melville, Rob Schuckard, and Adrian Riegen to capture birds at sites on both North and South Island and track them on their northward migration -- hopefully all the way to the breeding grounds. The aim of the project, however, is to learn specific stopover sites used during the northward flight.