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Scripps's Murrelet | Synthliboramphus scrippsi
Scripps' alk | Mérgulo de Scripps
Scripps's Murrelet is the small black-and-white auk of the California Channel Islands: invisible by day in a rock crevice, noisy by night, and for the rest of the year out at sea in pairs. Its chicks leave the nest two days after hatching, jump from the cliff into the sea in darkness and swim off with their parents into open water. Until 2012 it went with Guadalupe Murrelet as a single species; since then the two are kept apart in the classification.
Voice
The call at the colony is a loud, rapid series of six to eight evenly spaced seep notes on one pitch, a sound recalling a Pigeon Guillemot and carrying far over the water. Between them come short chip notes and thin whistles, with which partners call to each other on the water beside the island. All of it happens after sunset: by day the bird is mute, and even out at sea it is rarely heard. These calls were among the features that proved to sound different from those of Guadalupe Murrelet.
Recording: Matthew L. Brady — CC BY-NC-SA 4.0 · Crespi Knoll Seamount, United States · xeno-canto
Identification
A small auk with a small head, a thin pointed black bill, black upperparts and clean white underparts; the legs are bluish-grey. In fresh plumage the black of back and wings carries a blue-grey sheen, which later in the season fades to a dull brown. The black of the cap runs down to the level of the eye and no lower, so that the dark eye lies within the black; a small white crescent stands above and below it. The underwing is entirely white — a clear white flash as the bird takes off. Male and female are alike; the winter bird is a little greyer above, and juveniles carry scattered dark bars on the flanks.
Confusion species
Craveri's Murrelet (Synthliboramphus craveri) is the most similar: it has a dusky rather than a white underwing, a dark half-collar at the sides of the breast, and black running down below the eye. Guadalupe Murrelet (S. hypoleucus) shows more white in front of and above the eye, so the eye there sits in a white field instead of in the black cap. A winter Marbled Murrelet also looks black and white at range, but it has a white collar and a white bar on the shoulder and is stockier in build. It pays to make a bird fly: the underwing separates the two species that are all but inseparable on the water.
Habitat
It breeds on islands with steep cliffs and rocky slopes, laying its eggs in a crevice, a hole under a boulder or under a dense bush; it builds no nest. It feeds at sea, partly over the continental shelf and partly far beyond it, in the warm water of the California Current. It avoids the mainland shore and the bays, and sets foot on land only in the dark. On the breeding islands a dense layer of low shrubs matters: it roofs the crevices and keeps gulls at a distance.
Where the bird is most often found, arranged by the USNVC — the vegetation classification of the United States and Canada — and CMECS for sea and coast.
Range and movements
The breeding colonies lie on the California Channel Islands — Santa Barbara Island holds the largest — and on the islands off northwestern Baja California, from the Coronado Islands to the San Benito Islands. Off southern California the birds are present mainly from March to June; afterwards they move north, in some years into the waters off Oregon and Washington. Exactly where they winter is still poorly known, since they spend the season on the open ocean. On the San Benito Islands it breeds beside Guadalupe Murrelet without the two mixing to any real extent.
- Resident
- Breeding (summer)
- Passage
- dark = core range, pale = thinly spread
Where and when to look
In North America it can be seen on a day trip from Ventura or Oxnard to Santa Barbara Island in April or May: the pairs then float around the island by day and often let the boat come close. Look for two birds together on smooth water, not for a flock — this auk seldom flies in numbers. Anyone wanting to name one should wait for the underwing rather than judge by the head pattern.
Conservation
The world population is put at fifteen to thirty thousand birds and is falling; the IUCN treats the species as Vulnerable (VU). Introduced rats and deer mice take eggs, oil from the shipping lanes to Los Angeles is a standing risk, and warmer sea water shifts the food supply. After rats were removed from Anacapa Island in 2001 and 2002 breeding success there rose sharply — the clearest evidence that something can be done about this threat.
Scientific name
Synthliboramphus scrippsi | (Green; Arnold, 1939)
Green and Arnold published the name in 1939 as Endomychura hypoleuca scrippsi, that is, as a subspecies of Guadalupe Murrelet; because the form has since stood in another genus, author and year appear in parentheses. The genus name Synthliboramphus is built from Greek sunthlibo, 'to press together', and rhamphos, 'bill'. The epithet scrippsi is a latinised personal name, Scripps, from the circle of Californian ocean scientists at La Jolla; no separate type locality is recorded for this name in the source this guide follows. Only in 2012 was the form raised from subspecies to species, on the grounds of the absence of interbreeding on the San Benito Islands and of differences in facial pattern, bill shape, voice and genetic material.