storm petrel Oceanodroma tristrami, though the two species were later distinguished by size. Similarly, ornithologist Reginald Wagstaffe considered Tristram's storm petrel a subspecies of Markham's storm petrel in 1972, though subsequent research recognized them as different species. In 2016, the International Union for Conservation of Nature (IUCN) reclassified Oceanodroma markhami as Hydrobates markhami based on HBW and BirdLife International Illustrated Checklist of the Birds of the World, volume 1, by Josep del Hoyo and British ornithologist Nigel J. Collar. In some studies, the genus Oceanodroma was found to be paraphyletic with respect to Hydrobates, and all former Oceanodroma species were transferred to Hydrobates under some authorities. In 2021, all species in Oceanodroma were transferred to Hydrobates by the International Ornithologists' Union. Its name in Spanish is Golondrina de mar negra or paíño ahumado. Description Markham's storm petrel is an all-black to sooty brown storm petrel with a dull lead-gray gloss on its head, neck and mantle in fresh plumage. Its underside, from the neck down, and wing lining are blackish brown, and become almost fuscous, or brownish-gray, with wear of the plumage. External edges of wing coverts in the bird become whitish with wear, but are normally brown; the whitening produces a broad grayish bar that generally extends closer to the wing's bend than what American ornithologist Robert Cushman Murphy observed as a somewhat similar mark in the black petrel Loomelania melania (Procellaria parkinsoni). Markham's storm petrel's iris is brown, its bill and feet are black, and its tail is deeply forked. Two female specimens taken from in August 1967, both with small gonads and unused oviducts, had heavy contour molt and light fat. Murphy described the species as difficult to distinguish in life from the black petrel, with the chief difference being a much shorter tarsus. According to an average of six males and five females, adult males have a wingspan of compared to a wingspan of in adult females, and the tarsus is in adult males and in females. Tails are in adult males and in adult females. Sexes are alike in terms of physical description, and according to Drucker and Jaramillo of Birds of the World, there are "no known morphological differences between adults and juveniles", even in hand. Markham's storm petrel's eggs are described as pure white without gloss. Molting adults are seen in the southern spring and early summer, molting juveniles several months earlier. Ornithologists