Type: report

Article abstract: In 1995, a minimum of approximately 2,585-2,611 pairs of the endangered California least tern (Sterna antillarum browni) nested at 37 sites along the coast of California. This 7% decrease in breeding population size from 1994 brings to an end the trend since 1987 of continued growth of the population, and is likely attributable, at least in part, to the poor fledgling production experienced statewide in 1992. In addition to the drop in pair numbers, heavy predation pressure at many sites, an apparent shortage of food at two large sites, and a heavy storm in mid-June across the State, combined with a variety of human-related constraints on tern reproductive success, resulted in the lowest statewide fledgling-to-pair ratio recorded since fledgling production estimates were incorporated into monitoring protocol (1978). A minimum of approximately 963-1,174 fledglings was produced, 41% fewer than in 1994, resulting in a statewide fledgling per pair ratio of 0.37-0.45. As usual, successful and unsuccessful sites were distributed rather evenly throughout the State. Terns themselves were more unevenly distributed: 50% of the statewide population bred at only five sites (Venice Beach, Santa Margarita River/North Beach, Mission Bay/Mariner's Point and FAA Island, and Tijuana River/South); inclusion of an additional four sites (NAS Alameda, Bolsa Chica, Huntington Beach, and Delta Beach/North) accounted for 73% of all breeding pairs, and the inclusion of two more (Ormond Beach/Edison and Seal Beach) accounted for 81%. The fledglings produced at Santa Margarita River/North Beach, Mission Bay/Mariner's Point, and Delta Beach/North constituted 33% of the State total; the balance were distributed relatively evenly among sites.