Figure 69. An adult Red-billed Tropicbird photographed on Monterey Bay, Monterey County—where the species is very rare—in September 1998. This bird was found during an El Niño event that raised surface water temperatures in the eastern Pacific Ocean, increasing the chances of this tropical/subtropical species reaching central California (John Sorensen).

 

 

 

 

RED-BILLED TROPICBIRD Phaethon aethereus Linnaeus, 1758

Accepted: 0 (0%)	Treated in Appendix H: no
Not accepted: 1	CBRC review: 1973 records1
Not submitted/reviewed: NA	Color image: none

This tropicbird nests on tropical and subtropical islands of the Atlantic, Indian, and eastern Pacific Oceans. Near California, P. a. mesonauta breeds in the Gulf of California and on Rocas Alijos, off the Pacific coast of Baja California Sur. Small numbers of birds presumed to originate in western Mexican colonies occur regularly far off the coast of southern California, and irregularly closer to the mainland and northward to central California. The only acceptable California record north of Monterey Bay refers to a bird observed on 5 October 1979 about 112 miles off Pt. Arena, Mendocino County (AB 34:195, fide R. L. Pitman). This location was erroneously given as approximately 50 miles west of Ft. Bragg by Harris (2006), who considered the record hypothetical. Several birds have been reported in Oregon waters, but no records have been submitted for review by the Oregon Bird Records Committee. Even farther north, one was collected on 18 June 1941 at Westport, Washington.

Through a quirk of the review process, the CBRC did not accept any records of the Red-billed Tropicbird during the species’ brief stint on the review list. An old record of a skull from the “coast of Marin County” (Bryant 1888) cannot be confirmed (Grinnell and Miller 1944), so the state’s first record is of a bird collected in “the San Pedro Channel about midway between” Long Beach and Santa Catalina Island in August 1916 (Law 1919). This specimen was made into a life mount and, oddly, put on display in the Long Beach Chamber of Commerce building (Grinnell and Miller 1944). The earliest record with an extant scientific specimen refers to a bird collected on 27 June 1937 about 30 nautical miles west of San Clemente Island, Los Angeles County (Willet 1937, LACM 18778).

Briggs et al. (1987) reported 39 sightings of Red-billed Tropicbirds in southern California waters between April and January, most of them well beyond the Channel Islands. They found this species most consistently during the period July–September at Cortez Bank and Tanner Bank (roughly 38 nautical miles west of San Clemente Island’s southern tip), from there northwest toward San Juan Seamount, and between San Nicolas and Santa Rosa Islands. They also reported an apparent late-summer shift in distribution toward “the easternmost Channel Islands.” A noteworthy concentration of 15–20 birds off San Clemente Island on 29 July 2001 (NAB 55:482) raises the possibility that the species might eventually be found breeding in the state. Ainley (1976) and Briggs et al. (1987) hypothesized a potential foraging relationship between Red-billed Tropicbirds and tuna, but this was rejected by Ballance and Pitman (1999).

Living Red-billed Tropicbirds have twice been found in California’s interior following the passage of tropical storms from the Gulf of California through the Sonoran Desert (see Patten 1998): a second-fall female at Morongo Valley, San Bernardino County, 11 September 1976 (SBCM 56986), and an adult female south of Palo Verde, Imperial County, 27 September 1997 (SDNHM 49913). Three of Arizona’s five records (Rosenberg and Witzeman 1998) involve specimens. All of these interior specimens pertain to subspecies mesonauta (Patten et al. 2001).

 

¹On the review list 1972–1976