白头风暴海燕

Pelagodroma marina (Latham)

WHITE-FACED STORM PETREL

PELAGIC DISTRIBUTION.—Most POBSP pelagic records of this basically southern hemisphere hydrobatid are from west of the Galapagos Islands. Practically all sightings fall within a triangular area with points at 5°N, 112°W; 8°S, 112°W, and 3°S, 100°W (Figure 93). Two adult females were collected by the POBSP on 24 August 1967 at 6°19′S, 111 °55′W. Three other specimens taken in the eastern Pacific (two near the Galapagos, one near Ecuador) are mentioned in Murphy (1936:768). Lévêque, et al. (1966) report a specimen collected in September 1930 about 100 miles southwest of the Galapagos, and two sightings in August 1960 and seven sightings in July 1961 about halfway between the Ecuadorian mainland and the Galapagos.

The similarity of south Atlantic (Tristan da Cunha Islands) and south Pacific (Australia-New Zealand) subspecies makes it difficult to assign origin to specimens collected near the Galapagos. Murphy (1936:768), while implying that some form of this species was probably resident in the eastern Pacific, left the question of origin open. Most likely these eastern Pacific records pertain to members of the Australian-New Zealand populations, which migrate to the South American coast and follow the Peru Current north and west through the Galapagos region. The large number of records west of the Galapagos in August and September (84% and 14%, respectively, of total POBSP sightings for those months) indicate a buildup prior to the return to the Australian-New Zealand breeding grounds where egg-laying takes place in late October. The condition of our August specimens (in terminating stages of complete molt and with moderate fat) is in accord with the condition of other procellariiforms prior to a prebreeding migration. Murphy (1936) and Palmer (1962) summarize the known biology of the species.