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Eskimo curlew Listed: 3/11/1967 Status since listing: Extinct before listing The Eskimo curlew (Numenius borealis) is only known to have bred in two small, treeless areas in Canada's Northwest Territories, but is likely to have bred more widely there and possibly in the Yukon, Alaska and Siberia as well [1]. In autumn it migrated across a large swath of northern and eastern Canada, and New England (especially Massachusetts) to pampas of Argentina. Small numbers of migrating birds were occasionally seen in Michigan, Illinois, Ohio, New York, Pennsylvania, Maine, Rhode Island, Connecticut, New Jersey, Maryland, North Carolina, and South Carolina. The United States was of more importance to the spring migration which passed over Central America, eastern Mexico and the Gulf of Mexico, and the central states: Texas, Louisiana, Oklahoma, Missouri, Nebraska, Kansas, western Iowa, Illinois, western Minnesota, eastern South Dakota, and North Dakota. Birds also migrated across central and northern Alaska. Based on location, timing, and crude descriptions of the birds, some speculate that the Eskimo curlew and the American golden plover were the migrating land birds reported by Christopher Columbus on October 7, 1492 while several days out of sight from the shores of North America [3]. Columbus changed course to follow the birds, landing on San Salvador Island on October 12, 1492. The Eskimo curlew was seen in massive flocks during the 19th century [1]. Its total numbers were certainly in the hundreds of thousands, could well have exceeded a million, but probably fell short of the ten million sometimes reported. It declined catastrophically between 1870 and 1890 and was thought extinct between 1905 and 1945. The last documented nest was found in 1866, the last documented U.S. sighting in 1962, and the last documented sighting ever in 1963. There are only four photographs of live birds, all of the same pair on the same day in 1962. The curlew was placed on the endangered species list in 1967. Since then there have been sporadic, often disputed reports of isolated birds from Argentina to Texas, Maine, and Manitoba [1], the most recent by a well-credentialed shoreline birder on Martha's Vineyard, Massachusetts in 2002 [2]. While its remote breeding habitat remains intact, the curlew's tallgrass and eastern mixed-grass prairies habitats on the Great Plains were all but eliminated by agriculture and fire suppression [1]. Only 4% of the original 74 million ha of native tallgrass prairie remain. Historic prairie landscapes consisted of a shifting patchwork of habitats supporting immense insect populations and a diverse assemble of birds feeding on them. As fire was actively suppressed and passively hemmed in by agricultural patterns, it became unable to create new habitat patches as the older ones fell under the plow. Patches thus not only declined in extent, but grew farther apart and more difficult to find. Patch dynamics also increased the efficiency of commercial hunters who persecuted the curlew from 1860 until 1890 when it became too rare to support the industry. Hunting pressure was especially intense after the late 1870s when the extinction of the passenger pigeon forced hunters to concentrate on other prey. Though hunting was significant in some portions of the autumn migration route (especially Massachusetts), it was most intense on the Great Plains. As the habitat patches became small, curlew densities grew larger, allowing hunters to more efficiently kill them en masse. Hunting efficiency was also increased by efforts to eradicate the Rocky Mountain grasshopper by plowing up its eggs and nymphs. The freshly exposed grasshoppers drew enormous curlew flocks to hunters lying in wait. Within a span of fifty years, however, the Rocky Mountain grasshopper changed from one the most common large insects in the central and west central states to one of North America's most rapid extinctions. The loss of this massive, irruptive food source placed additional stress on a dwindling curlew population. While the combined effects of these factors led many bird species to decline, only the curlew was pushed to the brink, possibly further, of extinction. It seems likely that the curlew, like the passenger pigeon, was rendered vulnerable to extinction by the combination of flocking in very large groups, gathering in small habitat patches, and being simultaneously subjected to intense hunting and habitat loss [1]. For the purposes of determining its post-listing population trend, we censor the curlew as "extinct before listing" because it has not been documented since four years prior to being protected under the Endangered Species Act. On the bright side we note that several of the post-1967 sightings are intriguing enough to warrant continued searching. On the dark side, if the species still exists, its population must be very small and therefore facing an extraordinary extinction risk for a species evolved to exist in large flocks and migrate over 16,000 miles round trip. [1] Gill, R E., Jr., P. Canevari, and E.H. Iversen. 1998. Eskimo Curlew (Numenius borealis). In The Birds of North America, No. 347 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. |
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