Poor reproductive success has contributed to the decline and low population size of the federally listed Western Snowy Plover (Charadrius alexandrinus nivosus), especially where it breeds on coastal beaches used by humans for recreation. From 2001–2004, we compared reproductive success of color-marked plovers breeding on ocean beaches with those on gravel bars of the lower Eel River in coastal northern California, one of six recovery units as identified by the species' recovery plan. In three of four years, more plovers (54–64%) nested in river than beach habitats, but this pattern was reversed in the last year of the study when 62% of plovers used beaches. Each year, a higher proportion of clutches hatched and more chicks fledged from river than beach habitats, producing a disproportionate number of yearlings recruited into the local population from the river. On average, river-nesting males tended significantly fewer eggs, hatched similar numbers of chicks, and fledged significantly more young compared with males breeding on beaches. Corvids were more prevalent in river habitats in two of four years, but beaches consistently had significantly greater human activity. These habitat differences in reproductive success exist despite efforts to manage predators (e.g., exclosures around nests) and humans (e.g., signs, fencing, and vehicle restrictions) on beaches and almost no management of river habitats.
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Vol. 76 • No. 4