Type: report

Article abstract: In 1994, a minimum of approximately 2,792 pairs of the endangered California least tern (Sterna antillarum browni) nested at 36 sites along the coast of California. This 20% increase over 1993 breeding population size continues the trend since 1987 of continued growth of the population, and is directly attributable to the efforts of people working on behalf of recovery of the species. The statewide total of 2,792 pairs is the highest number recorded since systematic monitoring began in 1973, and represents a four-and-a-half-fold increase over the estimated 600 pairs of that year. Unfortunately, in 1994, heavy predation pressure at many sites and an apparent food shortage at two large sites, combined with a variety of human-related constraints on tern reproductive success, resulted in poor fledgling production statewide. A minimum of approximately 1755-1871 fledglings were produced, 11% fewer than in 1993, resulting in a statewide fledgling per pair ratio of 0.62-0.67. Documented and suspected predator species across the State ran the usual gamut; however, kestrels, crows, ravens, rats, and a peregrine falcon were responsible for the loss of the majority of terns and tern eggs lost to predation in 1994. As usual, successful and unsuccessful sites were distributed throughout the state. Terns themselves were more unevenly distributed: 48% of the statewide population bred at only four sites (Venice Beach, Huntington Beach, Santa Margarita River/North Beach, Mission Bay/FAA Island); inclusion of an additional five sites (NAS Alameda, Seal Beach, Bolsa Chica, Delta Beach/North, Tijuana River/South) accounted for 76% of all breeding pairs. And, again as usual, the bulk of fledglings produced statewide came from only a few sites; those produced at NAS Alameda, Venice Beach, Seal Beach, Santa Margarita River/North Beach, Mission Bay/FAA Island, and Delta Beach North comprised approximately 70% of the State total.