eWestern Birds

Changes in Winter Abundance of the Ruddy Turnstone Along the Coast of California

Edward R. Pandolfino and James W. Helmericks

ABSTRACT: We used data from Christmas Bird Counts (CBCs) to demonstrate a significant decline over the last 28 years of the Ruddy Turnstone (Arenaria interpres) population wintering along the coast of California. Of the seventeen CBCs with analyzable data, eight revealed significant decreases, but none revealed an increase. The average number of Ruddy Turnstones counted since 1990 has decreased by 43% compared to the average prior to 1990. Declines were noted on CBCs from north of San Francisco to San Diego. Older data from some of the California CBCs suggested that the higher numbers of turnstones recorded in the late 1970s and 1980s may have reflected a period of unusually high abundance, perhaps part of a cyclic change. Several factors may have contributed to the decrease of the Ruddy Turnstone in California. However, we suspect that the most important is climate change, possibly related to the long-term fluctuations of sea-surface temperature known as the Pacific decadal oscillation. There may have been a decline in the quality of intertidal habitats along the California coast, affecting wintering populations of the Ruddy Turnstone and possibly of the Wandering Tattler (Heteroscelus incanus).

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