| The Hayward Regional Shoreline, located along the eastern side of the San Francisco Bay, provides nesting habitat for two sympatric terns. The endangered California Least Tern nests in close proximity with a newly established Forster's Tern colony. Their diets overlap slightly. Kleptoparasitism by the larger Forster's Terns on California Least Terns has been observed at this location. Diet trend data, gathered by collecting dropped fish at both species' colonies in 2015 and 2016 showed they forage on members of the Gobiidae (gobies), Engraulidae (anchovies), Cyprinidae (goldfish) and Atherinopsidae (silversides) families. Statistical analysis using two-sample t-tests and chi-squared goodness-of-fit tests showed a significant difference between their diets, with silversides making up a much larger portion of the California Least Terns prey. To understand the effect of kleptoparasitism by Forster's Terns on California Least Terns, reproductive success data was collected at both colonies. Statistical analysis using unpaired t-tests revealed no significant difference in nesting or fledgling success between these two colonies. While kleptoparasitism may affect the individual fitness of a single bird in terms of time and energy spent avoiding parasitism, there is no statistical evidence indicating aerial "piracy" by Forster's Terns has resulted in negative effects on California Least Terns due to reduced food availability to their chicks, or their reproductive productivity at this site. |