Guadalupe Murrelet or Ancient Murrelet?

Here's how to tell the difference

Guadalupe Murrelet image 1

Guadalupe Murrelet

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Ancient Murrelet image 1

Ancient Murrelet

Guadalupe Murrelet

Synthliboramphus hypoleucus

Guadalupe Murrelet Recognition Guide

Guadalupe Murrelets are small seabirds known for their sleek black and white plumage. The upper parts of the bird, including the back and wings, are dark grey to black, providing excellent camouflage against the ocean. Their underparts are bright white, creating a stark contrast with their dark upper plumage. These murrelets have a short, pointed bill and relatively small wings, suited for both flying close to the water's surface and underwater diving. Their legs and feet are set far back on their body, which is advantageous for swimming but gives an awkward gait on land. There are no noticeable differences in plumage between male and female Guadalupe Murrelets, making sex identification challenging based solely on appearance. Both genders share identical coloration and markings throughout the year. Juvenile Guadalupe Murrelets differ from adults primarily in the subtlety of their plumage. Young murrelets tend to have softer and slightly duller coloration on their upper parts, with less defined contrast between the dark and light areas. As they mature, their plumage develops the sharper color contrasts characteristic of adults, aiding in camouflage and courtship displays during breeding seasons. Observing these birds in the wild involves looking for their distinct flying pattern, close to the water, and listening for their vocalizations, especially during twilight when they are most active.

Size

9.4 - 10.2 in/4.6 - 6.0 oz

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How to tell the Guadalupe Murrelet from the Ancient Murrelet

Visual differences

The Guadalupe Murrelet (S. hypoleucus) is smaller, weighing 4.6-6 oz and measuring 9.4-10.2 inches. It exhibits a contrasting black-and-white plumage, with a white face extending below the eyes, and a thinner, more pointed beak. The Ancient Murrelet (S. antiquus), slightly heavier at 6.3-9.5 oz and 9.4-9.8 inches long, features more distinctive black-and-gray plumage and a broader, blunter beak. Both birds present unique plumage patterns, yet the Ancient Murrelet’s "tuxedo-like" appearance is emblematic, providing a clear visual distinction between the species.

Key differences and behavior

The Guadalupe Murrelet and Ancient Murrelet exhibit distinct behavioral traits and habitat preferences. Guadalupe Murrelets are nocturnal, adept divers primarily in the cold Pacific waters near Baja California, feeding on small fish and crustaceans. They breed in rocky crevices with minimal nests, displaying courtship at dusk and fostering precocial chicks who dive soon after birth. Conversely, Ancient Murrelets, found from Alaska to Japan, also favor rocky coastal regions and thrive in dense colonies within forested islands. They demonstrate synchronized courtship and rely on surface-foraged small fish and plankton, breeding in late spring. These murrelets raise chicks entirely at sea, encouraging early independence. Guadalupe Murrelets remain closer to breeding grounds, while Ancient Murrelets can venture further, adapting to human-disturbed areas. Both share monogamous breeding and equal parental duties, yet differ in nesting environments and chick-rearing independence.

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