Type: report

Article abstract: Monitoring to document breeding success of California least terns (Sternula antillarum browni) continued in 2008, with observers at 36 nesting sites providing data. An estimated 6998-7698 California least tern breeding pairs established 8223-8226 nests and produced 2254- 2573 fledglings at 47 documented locations. The fledgling to breeding pair ratio was 0.29-0.37. Statewide, 13,847 eggs were reported, with a Site Mean clutch size of 1.77 eggs per nest (St Dev = 0.124) and the statewide clutch size of 1.75 eggs (St Dev = 0.452) for Type 1 sites (clutch sizes for each nesting site are provided for 2004-2008). Numbers of nesting least terns were not uniformly distributed across all sites. Camp Pendleton, Naval Base Coronado, Batiquitos Lagoon, Los Angeles Harbor, and Venice Beach represented 64% of the breeding pairs while Alameda Point, Venice Beach, Huntington Beach and Los Angeles Harbor produced 50% of the fledglings. The 2008 chick mortality rate of 14% represented the first increase since 2004 but the actual rate was less than those of 2004 (32%) and 2005 (28%). Camp Pendleton, Venice Beach, LA Harbor, Seal Beach, and Batiquitos Lagoon Ecological Reserve represented 87% of the total reported chick deaths, but only 45% of the total chicks. The main predator of least terns in 2008 was the American crow (Corvus brachyrhynchos), resulting from depredation of 760 eggs at Venice Beach. Gull-billed tern (Gelochelidon nilotica), common raven (Corvus corax), and coyote (Canis latrans) predation each comprised 8-10% of all predation. Common ravens, peregrine falcons (Falco peregrinus), American crows, gulls (Larus sp.), great blue herons (Ardea herodias) and American kestrels (Falco sparverius) were reported from the most sites. The monitoring effort of 2008 is scheduled to continue in 2009.