Magnificent Frigatebird Fregata magnificens
After fledging, a few immature Magnificent Frigatebirds sail north from their colonies in western Mexico, crossing the international border and reaching southern California as rare visitors in summer. Formerly, several were reported in San Diego County annually, but through last two decades of the 20th century this frequency decreased, until by the beginning of the new millennium the county was averaging only about one per year.
Migration: Magnificent Frigatebirds have been seen all along San Diego County’s coast and quite far out to sea. The atlas period had one in 1997, three in 1998, none in 1999 or 2000, and three in 2001. Late June to mid September is the species’ normal season. One at Mariner’s Point, Mission Bay (R7), 5 June 1998 (S. M. Wolf) and one off La Jolla (P7) 15 June 1996 (P. A. Ginsburg, NASFN 50:996, 1996) were exceptionally early; one along the Silver Strand (T9) 1 October 1977 (AB 32:256, 1978) was exceptionally late. An immature photographed on the ocean off San Diego 23 April 1989 (B. Archer, AB 43:536, 1989) was unseasonal.
There are six inland records, the most recent of one at Lake Henshaw 8 August 1983 (R. Higson, AB 38:246, 1984). The only frigatebird known from the Anza–Borrego Desert was over the Borrego Springs elementary school (G25) 25 June 1965 (ABDSP file). Unitt (1984) listed other inland records, most or all of which were of birds that reached the county by way of the Gulf of California or Salton Sea.
Winter: The three winter records are of one at National City (T10) 5 January 1992 (G. McCaskie, AB 46:314, 1992), one at Cardiff (L7) 1 March 2001 (R. Trissel, NAB 55:227, 2001), and one photographed at La Jolla (P7) 4 January 2002 (A. Mercieca, NAB 56:223, 2002).
Conservation: The number of frigatebirds reported in San Diego County peaked in 1979, when five were in the Tijuana River valley 20 July and five were at Lake Cuyamaca (M20) 2 August (AB 33:896, 1979, 34:200, 1980). Since then it has declined steadily. At 20,000 pairs in the 1980s, the colony on Isla Santa Margarita, Baja California Sur, is one of the species’ largest (Diamond and Schreiber 2002). But the concentration of the population on the Pacific side of Baja California into a single colony makes the birds vulnerable. Diamond and Schreiber (2002) attributed the frigatebird’s decline rangewide largely to disturbance at nesting colonies. They noted the frigatebird’s dependence on dolphins and tuna, themselves threatened, to drive small fish to the ocean surface where frigatebirds can seize them.