About Pterodroma defilippiana (Giglioli & Salvadori, 1869)
Masatierra petrel (Pterodroma defilippiana) grows to a length of about 26 centimetres (10 in). It has dark grey cap and mask, with a white forehead. Its upperparts are covered in dark grey plumage that bears a distinctive "M" mark; it also has a paler grey partial collar, and white throat, belly, and under wing-coverts. When viewed from below, its wings have black tips and black trailing edges.
Masatierra petrel spends most of the year at sea in the eastern Pacific Ocean south of the equator, where the Humboldt Current creates a major upwelling of nutrient-rich cold water. In this area, the bird feeds by skimming across the water surface and scooping up prey while flying. It nests in two island groups off the coast of Chile. On the Desventuradas Islands, the largest colony is located on San Ambrosio, where an estimated more than 10,000 birds were present in 1970. At that same time, San Félix hosted 150 to 200 nesting pairs. On the Juan Fernández Islands, the species is no longer thought to nest on Robinson Crusoe Island, while Santa Clara Island had a few hundred birds present in 1991. The population on Santa Clara Island is not expected to increase, due to the limited availability of suitable nesting sites there.
