|A Long-billed Curlew, banded at her nest in Nevada, will likely winter in the Central Valley. Photo by Nils Warnock/PRBO.|
Included in this spectacular birdlife are two species of conservation concern, the Long-billed Curlew and Mountain Plover, their numbers modest and their habitat vulnerable. During winter and migration, both aggregate on valley agricultural lands (far more than in coastal wetlands). They face threats to their habitats from urbanization and changing agricultural practices in California. To develop conservation strategies that succeed over the long term, better understanding these shorebirds' dependence on agricultural land is important, and PRBO is accomplishing this by focusing on the Long-billed Curlew.
Much remains to be learned about this large, striking shorebird. According to 2004-2005 estimates1, its global breeding population, restricted to western North America, numbers between 109,000 and 165,000 individuals. Very little is known, however, about where and in which habitats curlews spend some nine months of the year, after they finish breeding. The birds' abundance and habitat needs at sites where they "stage"2 during migration and settle for winter are among the aspects needing investigation.
One of the most important areas in the world for migrating and wintering Long-billed Curlews is known: California's interior valley region, with its vast expanses of dry and irrigated pastures, alfalfa fields, and rice fields. Surveys last September, of a sampling of California's inland agricultural land, tallied 29,434 curlews. Of these, about 65% occurred in the Central Valley, 35% in the Imperial Valley, and less than 1% in other regions. In the Central Valley overall, 17% of the birds were on wildlife refuges and fully 83% were on privately owned agricultural lands: alfalfa fields accounted for 42% of the total, irrigated pastures 37%. Curlews in the Imperial Valley were mostly in fields with grass crops or alfalfa.
Our September 2007 total represents 18%–27% of the North American breeding population, and we have covered only parts of the region so far. Many more curlews likely winter in the California interior valleys. Together with Audubon California and the Los Angeles Museum of Natural History (lead partners) and the many volunteer "citizen scientists" essential to this project, we will attempt more comprehensive surveys in the near future.
Effective conservation calls for understanding how Long-billed Curlews move and use habitat throughout their annual cycle, from their Great Basin and Great Plains breeding areas to Pacific coastal and interior areas where they stage for migration and spend winters. New technology makes it possible to follow birds like curlews worldwide, and PRBO is leading collaborative research using solar-powered satellite tags to map the migration patterns of large shorebirds throughout the Pacific Basin.
Last year we fitted these tags on seven Long-billed Curlews—two nesting in the Columbia Basin of northeastern Oregon and five in the Ruby Valley of Nevada. We successfully tracked all seven to wintering areas in California and Mexico.Three of the tagged curlews wintered in the Central Valley of California, where we were able to track their daily movements. This spring we tracked two Oregon birds and four Ruby Valley birds back to their original breeding locations! We expect to expand this project in 2008; watch for more discoveries about Long-billed Curlews in future Observers.
Our goal in this collaborative PRBO project is to acquire knowledge that will help us work with wildlife managers and the agricultural community, to provide habitat long into the future for curlews and other species dependant on agricultural lands.