The importance of Paracallisoma coecus and myctophid fishes to nesting fork-tailed and Leach's storm-petrels in the Queen Charlotte Islands, British Columbia

The diet of fork-tailed (Oceanodroma furcata) and Leach's storm-petrel (O.leucorhoa) was studied at Petrel Island, a small island north of Hippa Island in the Queen Charlotte Islands, British Columbia in 1983. The diet of the two storm-petrel species consisted mostly of the amphipod Paracallisoma coecus and fish. Most fishes which could be identified were myctophids, and may have been acquired by storm-petrels at night. Fishes increased while P.coecus declined in importance as a food over the nestling season of the storm-petrels. The amount of oil also declined in the Leach's storm-petrel diet over the season. Since P.coecus contains much oil, the seasonal decline of both P.coecus and oil was probably associated. Other less important foods were jellyfishes, copepods, isopods, euphausiids, shrimp, squid and octopus. Jellyfishes (Velella velella) only occurred in the diet of Leach's storm-petrels, which may relate to that storm-petrel feeding in open ocean where V. velella occurs most frequently. The most numerous copepod was Neocalanus cristatus, which was only observed in the storm-petrel diet early on during the study period. An abyssal copepod, Bathycalanus bradyi, and the isopod Cirolana californiensis (tentatively identified, the latter only previously known from sea canyons off California) were surprising food items of storm-petrels. Most euphausiid prey consisted of Thysanoessa spinifera and Euphausia pacifica.