Elliot’s Storm Petrel, Oceanites gracilis

Elliot’s Storm Petrel is a species of seabird in the family of storm petrels called Hydrobatidae. It may also be known as the White-vented Storm-petrel. The only two subspecies are; O. g. gracilis which is found in the Humboltd Current off of Peru and Chile, and O. g. galapagoensis which is found in the waters near Galapagos Islands. Its coloring is sooty-black with a white rump. Its legs are long and extend beyond the body when in flight. The tail is square ended and black except for a white bar that comes together with the white tipped rump to form an obvious white crescent shape.

Although there are many sightings of this bird, little is known about it. The only nests ever found were in Isla Chungungo, Chile, but it’s also thought that Elliot’s Storm Petrel also breed on small rocky islets from Chile north to the Galapagos. Until recently, only a single nest has ever been found. In 2003, nearly 11 more were found in rocky crevices. Nothing is known about the appearance of the nest except that the first nest ever found in 1979 consisted of scraps of vegetation underneath low plants. The Galapagos subspecies’ feeding habit is unusual amongst storm petrels because it hunts close to the shore; all other storm petrels are entirely pelagic. Because of examinations of dead birds from the Galapagos, it is believed that the eggs are laid during the Austral winter from April to August.

Keeping in common with several other species of storm petrels’ feeding behavior, Elliot’s Storm Petrel flutters over the surface of the sea, looking like it’s “walking on water”, searching for plankton and scraps of fish killed by larger predators. Their unusual technique is assumed to be the origin of the name petrel, coming from the biblical account of St. Peter walking on water. They rarely ever venture more than 100 kilometers from the shore and they are most abundant in cool, flooded waters.

It is suspected that there must be a breeding population of several thousand O. g. galapagoensis on the Galapagos. It is classified at Data Deficient (DD) on the IUCN Red List. On the tiny island of Chungungo, it is unlikely to support undiscovered nest sites, although rats, fire, Humboldt penguins, and short-tailed snakes have been quoted to be potentially responsible for the absence of a larger petrel population.

Image Caption: Elliot’s Storm-petrel Oceanites gracilis. Galapagos Islands. Credit:  Putney Mark / Wikipedia (CC BY-SA 2.0)