Lafferty Kevin D, Rodriguez Donald A, Chapman Angela
Western Ecological Research Center, US Geological Survey c/o Marine Science Institute, University of California, Santa Barbara, CA 93106 USA.
Springerplus. 2013 Dec;2(1):38. doi: 10.1186/2193-1801-2-38. Epub 2013 Feb 6.
Southern California's beaches can support a remarkable diversity of birds along the Pacific Flyway. We asked whether seasonal, annual, and spatial factors affect bird richness and abundance on public beaches. To do so, we conducted three years of monthly bird surveys on 12 sandy beaches in Ventura California. Across all surveys, we counted 22 shorebird species, 8 gull species, 24 other water bird species, and 24 landbird species. Sanderling, western gull, Heerman's gull, willet, marbled godwit, and whimbrel were the most abundant members of the bird community. Beach wrack was uncommon, particularly where beaches were groomed, and did not have a large effect on bird abundance, though it was positively associated with overall bird richness. Beaches near estuaries tended to be wide, and such beaches had a higher richness and abundance of birds. Beaches with shallow slopes tended to have more gulls and shorebirds. People and (illegal) unleashed dogs were common, particularly at beaches fronted by houses. The abundance and richness of shorebirds and the richness of other waterbirds was lower where human activity was high. Bird richness and abundance was strongly affected by season, with the highest density of birds being seen during the fall shorebird migration. Gull abundance peaked earlier (August-September) than shorebird abundance (October through December). A brief pulse of shorebirds also occurred in May due to spring migration. Comparing these data with surveys in the 1990's found no evidence for a decline in shorebirds over time, though black-bellied plover appear to still be recovering from the strong 1997-1998 ENSO. Opportunities to conserve birds on these beaches are limited, but could include enforcing leash laws and setting up human exclosures near estuary mouths.
南加州的海滩能为沿太平洋迁徙路线的鸟类提供极为丰富的多样性栖息地。我们研究了季节、年度和空间因素是否会影响公共海滩上鸟类的丰富度和数量。为此，我们在加利福尼亚州文图拉市的12个沙滩上进行了为期三年的月度鸟类调查。在所有调查中，我们统计到22种滨鸟、8种鸥类、24种其他水鸟和24种陆鸟。三趾滨鹬、西部鸥、黑背鸥、长嘴鹬、斑尾塍鹬和大杓鹬是鸟类群落中数量最多的成员。海滩漂浮物并不常见，尤其是在经过清理的海滩上，虽然它与鸟类的总体丰富度呈正相关，但对鸟类数量的影响不大。河口附近的海滩往往较宽，这类海滩上鸟类的丰富度和数量更高。坡度较浅的海滩往往有更多的鸥类和滨鸟。人和（非法）未拴绳的狗很常见，尤其是在有房屋的海滩前。在人类活动频繁的地方，滨鸟的数量和丰富度以及其他水鸟的丰富度较低。鸟类的丰富度和数量受季节影响很大，秋季滨鸟迁徙期间鸟类密度最高。鸥类数量的峰值出现得比滨鸟（10月至12月）更早（8月至9月）。由于春季迁徙，5月也出现了一小波滨鸟。将这些数据与20世纪90年代的调查进行比较，没有发现滨鸟数量随时间下降的证据，不过黑腹鸻似乎仍在从1997 - 1998年强烈的厄尔尼诺现象中恢复。在这些海滩上保护鸟类的机会有限，但可以包括执行牵绳法律以及在河口附近设置人类禁区。
