Markham's storm petrel

Appearance

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". 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 172.7 millimetres compared to a wingspan of 169.8 millimetres in adult females, and the tarsus is 23.9 millimetres in adult males and 24.2 millimetres in females. Tails are 92.7 millimetres in adult males and 89.4 millimetres 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 Larry B. Spear and David G. Ainley report that Markham's storm petrel has a more leisurely flight pattern than that of the black petrel, and state that Markham's storm petrel has a similar flight pattern to Leach's storm petrel. In 1980, Canadian author RGB Brown stated the birds tended to glide over two observations, with shallow and rapid wingbeats, though an observation by American ornithologist Rollo Beck described its wingbeats as slow, and slower than the wingbeats of Wilson's storm petrel "Oceanites oceanicus" and Elliot's storm petrel "Oceanites gracilis". Unlike the black petrel, Markham's storm petrel typically flies greater than one meter over the ocean surface.

Distribution

Markham's storm petrel inhabits waters in the Pacific Ocean around Ecuador, Peru, and Chile, though sightings have occurred on the equator west of the Galápagos Islands, within the Panama Bight, and off of Baja California. Sightings off of Baja California might mistake Markham's storm petrel for the black storm petrel due to difficulties of distinguishability in the field. Spear and Ainley observed Markham's storm petrel from to, which expanded its westward range from a compilation of sightings recorded by ornithologist Richard S. Crossin in 1974. Its presence is highly unlikely in the Atlantic Ocean outside of freak vagrancies, and in 2007, Spear and Ainley classified the species as endemic to the Humboldt Current. Despite its range, Markham's storm petrel only nests in Peru and Chile.

A survey conducted by Spear and Ainley from 18°N to 30°S, west to 115°, found greatest densities of the bird during austral autumn offshore between Guayaquil and Lima. During spring, the breeding population splits into two around southern Peru and northern Chile, stretching out 1,700 km offshore. Nesting colonies were first reported in the late 1980s to early 1990s. In 1992, 1,144 nests, equal to a population of approximately 2,300 nesting pairs, were found five kilometres inland on Paracas Peninsula in Peru. Two separate discoveries occurred in Chile in 2013: one of nesting sites south of the Acha valley es in Arica Province by a group of ornithologists and one of a recording of a bird singing by a biologist working for a consulting company. After further exploration in November 2013 based on the recording, in 2019, populations of 34,684 nests in Arica, 20,000 nests in Salar Grande, and 624 nests in Pampa de la Perdiz were found in the Atacama Desert of northern Chile. This translated to about ninety-five percent of the known breeding population at the time.

Behavior

External mediaAudio from the Cornell Lab of Ornithology's Macaulay LibraryVideo from Macaulay Library
Markham's storm petrel nests in burrows, natural cavities, and holes in saltpeter crusts. Nests in saltpeter cavities have been reported in Pampa de Camarones in northern Chile, and inland on Paracas Peninsula. In Peru, egg laying occurs from late June to August; in Chile, an analysis of three colonies in the Atacama Desert found a five-month reproductive cycle, from arrival at colonies to departure of fledglings, across all three colonies, though pairs could reproduce asynchronously. This could lead to an overall ten-month reproductive season. Pairs produce one egg per season, and adults in nests were found to vocalize when a conspecific recording of vocalizations was played at the entrance to the nest. The average incubation period in Paracas is 47 days. Both the female and male engage in duties related to incubation. The shifts in incubation lasted three days or less in Paracas. According to "Birds of the World", there are "[n]o details on the breeding colonies in Chile".

Mean width of the widest part of openings to nest burrows in Chile was measured at 10.3 centimetres with a standard deviation of ± 3.1 centimetres, with the narrowest part measured at 6.8 centimetres with a deviation of ± 1.9 centimetres. The average depth of the burrows was greater than 40 centimetres. After hatching, in Chile, the fledglings move towards the sea after a chick phase. Fledglings are either attracted to or disoriented by artificial lights, an occurrence common to burrow-nesting petrels.

In a study by Spear, Ainley and William A. Walker of the National Marine Mammal Laboratory, a sample of fifteen Markham's storm petrel had consumed namely the fish "Diogenichthys laternatus" and "Vinciguerria lucetia", among other foods. Markham's storm petrel was found to have a lower dietary diversity than other small petrels, though dietary diversity was high generally among small petrels compared to other birds analyzed. A 2002 study in "Marine Ornithology" found its main diet by mass consisted of fish, cephalopods, and crustaceans, with about ten percent of analyzed stomach contents suggestive of scavenging. Based on large variations in the types of food it consumes, and its tendency to scavenge, biologist Ignacio García-Godos concluded Markham's storm petrel was a forager which opportunistically found food near the surface of the ocean. The proportion of birds that feed or rest, compared to flying in transit, was significantly higher in austral autumn than spring in Spear and Ainley's 2007 study.

In 2018, researchers Patrich Cerpa, Fernando Medrano and Ronny Peredo found the ectoparasite stick-tight flea "Hectopsylla psittaci" on two birds out of ten captured in Pampa de Chaca within the Arica y Parinacota Region. Both specimens were found in the lorum on each bird. The turkey vulture "Cathartes aura" served as a possible source for the transition between hosts, as Cerpa, Medrano and Peredo observed the two nesting in the same colony. Researchers Rodrigo Barros et al. described the bird as "one of the least known seabirds in the world".

Habitat

Markham's storm petrel inhabits waters in the Pacific Ocean around Ecuador, Peru, and Chile, though sightings have occurred on the equator west of the Galápagos Islands, within the Panama Bight, and off of Baja California. Sightings off of Baja California might mistake Markham's storm petrel for the black storm petrel due to difficulties of distinguishability in the field. Spear and Ainley observed Markham's storm petrel from to, which expanded its westward range from a compilation of sightings recorded by ornithologist Richard S. Crossin in 1974. Its presence is highly unlikely in the Atlantic Ocean outside of freak vagrancies, and in 2007, Spear and Ainley classified the species as endemic to the Humboldt Current. Despite its range, Markham's storm petrel only nests in Peru and Chile.