Reassessment of a Western Hemisphere Shorebird Reserve Network Site: Kachemak Bay, Alaska

Two portions of Kachemak Bay, Mud Bay and Mariner Park on the Homer Spit and the Fox River Flats, Alaska, are recognized collectively as a site of International Importance for shorebirds within the Western Hemisphere Shorebird Reserve Network (WHRSN). These sites were designated based on observations collected between the 1970s and 1990s that indicated more than 100,000 shorebirds stopped at the sites each spring during their northbound migration. As part of an effort to assess shorebird use of this area, the Kachemak Bay Birders (KBB), a volunteer citizen-science organization, conducted ground surveys along Homer Spit and nearby waters between 2009 and 2011. They also conducted a series of aerial surveys along the Kachemak Bay coastline in 2010. After restricting data to areas and time periods comparable to historic data, we found the average number of birds observed from the ground on the Homer Spit was down by one-third compared to previous counts (18,436 prior to 1995 versus 7,055 observed between 2009 and 2011). Most of this change was due to a drop in the number of Western Sandpipers Calidris mauri, the most numerous shorebird species observed. Numbers of other species fluctuated from year to year but not as much, and the overall species composition remained the same although several new species were observed in low numbers. Contemporary aerial surveys indicated a large qualitative decline in the number of birds on the Fox River Flats relative to aerial surveys conducted during the 1970s–1990s. We discuss the possibilities that these changes represent a temporary decline, a decrease in the use of the area, a reduction in population size of the more common species, or just an artifact of changing methodologies. We also discuss issues to consider when reassessing a WHSRN (or other) designation should contemporary surveys show its declining importance to birds. Finally, we advocate for a broader-based survey within Cook Inlet and along the Pacific Flyway to better understand the trends observed at Kachemak Bay.