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The California Least Tern (Sterna antillarium browni) was listed as Endangered in 1970 due to direct and indirect impacts of human activities. According to a recent review by the U.S. Fish and Wildlife Service in 2006, the California Least Tern nesting population is increasing due to intense predator control although reproductive output remains very low. Due to the increase in nesting, it has been recommended to downlist the species to Threatened although the species is “conservation reliant”, and dependent upon site specific management and habitat protection. To date, there have been limited studies focusing on quantifying the relative influence of direct (loss of habitat) and indirect (changes in prey base) human impact of the reproductive output of the CLT. Least Terns are directly affected by shoreline development and human use of suitable breeding sites, but there has also been an increase in chick mortality that may be associated with indirect effects of human activity. The exact cause of this decline in breeding success is not clearly understood; suggestions include shifting weather patterns affecting sensitive breeding stages to changes in prey abundance, distribution and/or spawning patterns, and the destruction of breeding habitat by human activity. The goal of this project is to evaluate two possible factors that may influence vital rates of California Least Terns - foraging habitat quality and changes in prey base.   
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