California Least Tern Breeding Survey 2010 Season

Type: report

Article abstract: Monitoring to document breeding success of California least terns (Sternula antillarum browni) continued in 2010, with observers at 41 nesting sites providing data. An estimated 6437-6699 California least tern breeding pairs established 6968 nests and produced 1971-2245 fledglings at 51 documented locations. The fledgling to breeding pair ratio was 0.29-0.35. Statewide, 12,826 eggs were reported, with a Site Mean clutch size of 1.82 eggs per nest (St Dev = 0.198) and the Statewide clutch size of 1.84 eggs (St Dev = 0.441) for Type 1 sites. Numbers of nesting least terns were not uniformly distributed across all sites. Camp Pendleton, Naval Base Coronado, Pt. Mugu, Batiquitos Lagoon, Bolsa Chica Ecological Reserve and Huntington Beach represented 73% of the breeding pairs while Camp Pendleton, Huntington Beach, Alameda Point, Naval Base Coronado and Batiquitos Lagoon Ecological Reserve produced 68% of the fledglings. The 2010 chick mortality rate of 18% is slightly greater than the last two years. Seal Beach, North Island Maintenance and Training Facility (NIMAT), Camp Pendleton, and Naval Base Coronado represented 73% of the total reported chick deaths, but only 56% of the total chicks. The predators responsible for the greatest number of depredated least terns in 2010 were gull-billed terns (Gelochelidon nilotica), common ravens (Corvus corax), coyotes (Canis latrans) and American crows (Corvus brachyrhynchos). Peregrine falcons (Falco peregrinus), great blue herons (Ardea herodias), common ravens, red-tailed hawks (Buteo jamaicensis), American crows, and western gulls (Larus occidentalis) were reported from the most sites. The monitoring effort of 2010 is scheduled to continue in 2011.

Number of pages: 72

Authors: Marschalek, Dan;

Day: 18

Month: July

Year: 2011

Publisher: California Department of Fish and Wildlife

Prepared for: California Department of Fish and Wildlife;

Keywords: endangered species; least tern;

Species: California least tern