San Luis National Wildlife Refuge Complex
San Luis National Wildlife Refuge Complex, which consists of three National Wildlife Refuges, is recognized as both an Audubon Important Bird Area and a Western Hemisphere Shorebird Reserve Network site. The 42,000 acres of the San Luis Complex are internationally acclaimed as significant shorebird habitat. The refuges are the primary wintering ground for the largest populations of Ross's Geese and 'Lesser' Sandhill Crane in the Pacific Flyway.
Invasive yellow starthistle rapidly forms dense impenetrable stands, particularly in disturbed areas. Yellow starthistle is best adapted to open grasslands, and able to complete its life cycle earlier than native perennials, allowing it to use up available water and outcompete native plants. As a result, yellow starthistle has eliminated thousands of acres of native habitat within the San Luis Refuge Complex.
The yellow starthistle problem increased at San Luis NWR over the past decade due to drought conditions. Today, yellow starthistle, along with perennial pepperweed, affects 65 percent of the refuge's uplands. In the past two years, the refuge has spent $150,000 to control the weeds using techniques such as prescribed fire, grazing, mowing, and herbicide application. In 2008, these methods were used to treat 18,800 acres. Despite these efforts, less than 2 percent of the acres treated are considered to be controlled and there is a constant surveillance program for re-infestation. There is some good news--the amount of invasive water hyacinth on the refuge is decreasing.
Threat to Birds
The Long-billed Curlew is threatened by the loss and degradation of prairies and meadows, which are needed for winter habitat. Long-billed Curlews have declined significantly in the past 150 years and are considered vulnerable throughout their range. The declining Long-billed Curlew population is further threatened by the exponential spread of yellow starthistle, which is taking over valuable wintering habitat on the San Luis Refuges.