|Population||7,500 (2012 est.)|
The Guadalupe murrelet (Synthliboramphus hypoleucus) is a small seabird of the family Alcidae, and found on the western coast of North America.
The Guadalupe murrelet is a small, relatively slim alcid, with a body length of 7.9-9.4 inches, a wingspan of 17.7-18.1 inches, and a body weight of up to six ounces. Females are slightly heavier than males. The legs set very far back on the body, giving it an awkward appearance on land.
The top is completely black. Freshly grown plumage has a slightly bluish luster, while worn plumage looks greyish. The bottom is white, with the white area extending up the throat to the sides of the head, and giving the brown eyes a white border. The small and pointed beak is black. The legs and toes are slightly bluish, the webs are black. Guadalupe murrelets fly with a fast wing beat, and can go to flight from the surface of the water with barely a ripple.
Young birds resemble adult birds, but have faint tufts on the flanks and a slightly shorter beak than adult birds.
This bird was once known as Xantus's murrelet, first described in 1859 by John Xantus de Vesey, a Hungarian naturalist and zoologist who did a detailed, if somewhat plagiarized, account of his travels in Baja California, and it was there that he collected and described many plant and animal species unknown to science at that time, including the murrelet named for him. The bird was recognized as having two subspecies:
- Synthliboramphus hypoleucus hypoleucus, Guadalupe murrelet
- Synthliboramphus hypoleucus scrippsi, Scripp's murrelet
In 2012 the American Ornithologists Union formally separated these birds into two distinct species in their own right, based on genetic and physical differences, lack of inter-breeding, and separated nesting sites.
This species has the southernmost distribution area among all alcids. Breeding areas are located only on Guadalupe and San Benito islands off the coast of Baja California, Mexico. The Guadalupe murrelet thus adheres to waters whose surface temperature is more than 12 degrees Celsius. Outside the breeding season, it lives on the open sea with a range north to central British Columbia southward to the tip of Baja California.
The colonies are found on small, low-precipitation islands with sparse and mostly thorny vegetation. Most colonies are less than 600 feet from the coastline. The birds are monogamous, and mate for life. In one study, birds that were leg-banded used the same nesting site three years in a row. The individual nests are spread out, which is rather uncommon for alcid birds, which often breed in dense colonies.
Guadalupe murrelets nest in small dugout holes, in rock niches, or under bushes. They also use abandoned burrows of rabbits and burrowing owls. The propagation time is relatively little synchronized. One study showed that Guadalupe murrelets lay 80 percent of the eggs over a period of 24 to 47 days. The earliest laying taking place on this island on February 22, with a peak in the period from March 21 to April 21. The last eggs were laid in the middle of June. The eggs are elliptic to oval and speckled grayish brown on a whitish to olive brown base and roughly speckled. Egg incubation usually begins two days after the second egg is deposited. The brooding period is an average of 31 days.
Captive Guadalupe murrelets changed their behavior within two days after hatching. While they remained calm in their nest until then, they showed a very agile behavior and ran agitated in their nest boxes. Under natural conditions, they are at that time led by the parent birds to the sea. They are already very good swimmers and on land able to climb over obstacles. Their further development on the high seas is not yet known. Captive birds showed only a very slow weight gain and a change in the plumage on the 17th day of life.
Gulls, owls, and falcons are among the natural predators, but the greatest impact in losses were made by introduced mammals to the islands via shipwrecks: rats and feral cats, which caused a decline in numbers on its breeding islands; a program meant to remove non-native predators from their islands is somewhat successful, giving hope that the species can recover.