Bristle-thighed Curlews Numenius Tahitiensis Research Articles

Population trends, size, and potential threats to Bristle-thighed Curlew Numenius tahitiensis: new data from French Polynesia

Summary Based on censuses in 2021 and 2022 of Bristle-thighed Curlews Numenius tahitiensis on 10 atolls of French Polynesia, the species has declined by c.50% over the last two decades. While the species has recently been down-listed from “Vulnerable” to “Near Threatened”, these new data would qualify it for an “Endangered” Red List status. The non-breeding population on Tuamotu numbers approximately 1,000 curlews and up to 1,500 individuals in all of Eastern Polynesia. On uninhabited islands, the expansion of copra (coconut pulp) exploitation has caused long-term disturbance for curlews, increased predation by pet dogs, and introduced or reinforced non-native rat populations. Climate change, particularly sea-level rise, will add to changes in land use that shrink the suitable habitat for Bristle-thighed Curlews in French Polynesia. As this study shows, obtaining population trends for species breeding in remote areas may best be achieved through surveys at key non-breeding sites.

Through thick and thin: Sexing Bristle-thighed Curlews Numenius tahitiensis using measures of bill depth

Through thick and thin: Sexing Bristle-thighed Curlews Numenius tahitiensis using measures of bill depth

Land birds of Tuamotu Archipelago, Polynesia: relative abundance and changes during the 20th century with particular reference to the critically endangered Polynesian ground-dove ( Gallicolumba erythroptera)

We report relative abundances and distributions of land bird communities on eight isolated islands of the Tuamotu Archipelago (Polynesia, South Pacific Ocean) during two 21-day expeditions in 1999. The selection of islands was based on the historical range of the Polynesian ground-dove ( Gallicolumba erythroptera), in the hope of finding populations of this critically endangered species. Data were also collected on the Tuamotu sandpiper Prosobonia cancellata, the Atoll Fruit-dove Ptilinopus coralensis, the Tuamotu reed-warbler Acrocephalus atyphus, the Spotless Crake Porzana tabuensis and the Bristle-thighed Curlew Numenius tahitiensis, and on introduced predators (cats, rats, pigs and dogs). None of the five land-bird species recorded previously, in 1922 and 1974, has completely disappeared, but ranges of several species have contracted. Only one population of G. erythroptera erythroptera was found and it is the only population known for this species today. Our data also raise particular concern for the future of the Tuamotu sandpiper.

The status of seabird colonies on the Cook Islands atoll of Suwarrow

Suwarrow (Suvorov) atoll is an important seabird breeding site in the central Pacific Ocean. However, it is not protected and is attractive to developers of potentially damaging aquaculture industries. In this paper I report the results of a survey conducted to establish the present status of Suwarrow's seabird colonies and to generate base-line data for measuring the effect of a proposed pearl-farm development. Between late July and early September 2000 the reef islets were surveyed for seabird chick numbers and age-states using a simple sampling method. In addition to Sooty Tern Sterna fuscata, populations of boobies Sula spp., noddies Anous spp., frigatebirds Fregata spp. and tropicbirds Phaethon spp. were assessed. Results showed that bird populations were maintaining levels similar to those from findings of surveys in 1992. Of particular note were globally significant numbers of Lesser Frigatebird Fregata ariel and Red-tailed Tropicbird Phaethon rubricauda. Migratory birds were observed with Bristle-thighed Curlew Numenius tahitiensis regularly seen. The well-being of bird-life on the islets appears to be indirectly proportional to the proximity of human activity, with birds not observed breeding on Anchorage Island – the islet most often visited by people.

Phenotypic Flexibility during Migration: Optimization of Organ Size Contingent on the Risks and Rewards of Fueling and Flight?

Avian long-distance migration involves the storage and expenditure of very large fuel loads. Birds may double in weight before take-off on flights of many 1000 km, and they may lose half their body mass over the subsequent few days that such trips take. Recent studies indicate that in addition to the storage and depletion of fat, the muscles and belly organs also undergo considerable changes in size in the course of such migrations. Such intraindividual and repeatedly reversed changes in stores and organ sizes represent a class of phenotypic plasticity called 'phenotypic flexibility'. Using preliminary comparative data for different populations of Bar-tailed Godwits Limosa lapponica, and several other shorebird species adding variation to the migration strategies sampled (Golden Plover Pluvialis apricaria, Ruff Philomachus pugnax, Red Knot Calidris canutus and Bristle-thighed Curlew Numenius tahitiensis), the thesis is developed that the size of the organs carried during take-off represent evolutionary compromises between their functions during the storage, flight and post-arrival phases of migration. In all cases fat-free tissue along with fat is deposited during fuel storage, but the proportions vary a great deal between similarly sized species. Just before departure on long-distance flights, exercise organs (pectoral muscle and heart) tend to show hypertrophy and nutritional organs (stomach, intestine and liver) tend to show atrophy. Reductions in nutritional organs appear most pronounced in (sub-) species that are about to overfly barren oceans with few or no opportunities for emergency landings. Migrant birds seem to show a great deal of adaptive flexibility, and the study of this flexibility may shed light on (presently unknown) physiological mechanisms as well as on correlated ecological constraints on bird migration.

Conservation problems and research needs for Bristle-thighed Curlews Numenius tahitiensis on their wintering grounds

SummaryThe Bristle-thighed Curlew Numenius tahitiensis is a rare shorebird that breeds in western Alaska and winters on oceanic islands in the tropical and subtropical Pacific Ocean. Before human colonization, the islands on which curlews winter were devoid of terrestrial predators, allowing curlews to evolve a rapid moult during which about 50% of adults become flightless. Especially when flightless, these birds are vulnerable to harvest by humans and to predation by introduced mammals such as dogs and cats. On atolls where they are harvested by humans, curlews tend to occur only on uninhabited islets. Consequently, human encroachment in Oceania has probably reduced Bristle-thighed Curlew numbers and altered winter distribution of the species. Future studies should (1) identify concentrations of wintering curlews, focusing in the Tuamotu Archipelago; (2) determine whether migratory stopover sites exist in the central Pacific between Hawaii and the southern end of the wintering grounds; and (3) establish a monitoring programme to assess population trends in several parts of the winter range. A comprehensive plan is needed to provide for the existence of predator-free islands throughout key portions of the winter range.