Low reproductive success of Black Skimmers associated with low food availability

Black Skimmers (Rynchops niger) have undergone an extended population decli ne over much of their range, including the coast of Virginia, USA, where th e population has decreased by 80% in the last two decades. A combination of starvation, flooding, predation and human disturbance has been cited as th e cause of low reproductive success. This study tested the hypothesis that, at a colony on an artificial island in the James River, Hampton County, VA , a shortage of food was responsible for the chronically low success of bre eding skimmers at a site protected from flooding, predation or human distur bance. Parents that fed more fledged a higher proportion of nestlings, sugg esting a relationship between food and chick survival. Abundance of one of the two primary prey species underwent a regional decline during the skimme r breeding season, and both primary prey species began seasonal declines be fore most skimmer chicks had fledged. Both of these fish species have also undergone long-term declines in the region and their annual abundance has b een closely correlated with regional skimmer numbers. Mortality of eggs nas low (30%) while mortality of chicks war high (70%), and nestling growth ra te and size at fledging appeared to be lower at this sire than published da ta would indicate was the case at other sites, all consistent dth the hypot hesis that starvation was occurring Finally, first-hatched chicks were more likely to survive than were their siblings, consistent with starvation as a primary cause of death.