Buller’s Shearwater
Buller's Shearwater
Ardenna bulleri
At a Glance
A cleanly patterned seabird, nesting only near New Zealand but visiting waters off the west coast of North America in fall. Buller's seems more buoyant and graceful in flight than most shearwaters, with more gliding and less flapping. It often arcs up high on one wingtip and then the other, and small flocks may turn and glide over the waves in unison.
All bird guide text and rangemaps adapted from Lives of North American Birds by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Gull-like Birds, Shearwaters and Petrels
IUCN Status
Vulnerable
Habitat
Open Ocean
Region
Alaska and The North, California, Northwest, Western Canada
Behavior
Flap/Glide
Population
1.700.000
Range & Identification
Migration & Range Maps
Breeding adults move north in May, common in parts of North Pacific in summer, returning to New Zealand waters by September. Seen off Pacific Coast of North America mainly June to November, most common September-October; evidently these are mostly nonbreeders and immatures.
Description
17" (43 cm). W. 39 (99 cm). Beautiful clean pattern, bright white below with underwings almost entirely white, gray above with black pattern (like a wide, flat M) across wings, sharp black cap. Much more contrasty than other western shearwaters. Looks long-tailed and long-winged, flies with long buoyant glides.
Size
About the size of a Crow, About the size of a Mallard or Herring Gull
Color
Black, Gray, White
Wing Shape
Broad, Pointed, Tapered
Tail Shape
Pointed, Rounded, Wedge-shaped
Songs and Calls
Silent at sea.
Call Pattern
Flat, Rising, Undulating
Call Type
Odd, Raucous, Scream
Habitat
Open ocean. Tends to concentrate at areas of strong upwelling, or where warm and cool water currents meet, bringing food to the surface. Rarely comes close to shore. Nests on islands with soil suitable for burrows or with crevices among rocky cliffs.
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Behavior
Eggs
One. White. Incubation is by both sexes, roughly 51 days.
Young
Both parents feed young, by regurgitation. Period from hatching to departure from nest probably about 100 days.
Feeding Behavior
Food is taken at or just below surface of water. Forages by dipping to surface in flight, plunging into water from a few feet above surface, swimming with head submerged, sometimes up-ending with head down and tail up. Rarely dives underwater. May feed at night.
Diet
Crustaceans, fish, squid. Diet not well known. Near breeding grounds may feed mostly on euphausiid shrimp and other crustaceans. Off California, may eat mostly small fish and squid.
Nesting
Breeds on Poor Knights Islands off North Island, New Zealand. Adults arrive there in September, most eggs laid in late November, young depart in May. Breeds in dense colonies. Adults noisy around colonies at night, may climb up into trees to take flight more easily. Nest: Site is in burrow under tree roots or rocks, or in cave or rock crevice. Both sexes help dig burrow. Nest chamber is lined with leaves, twigs, pebbles. Where birds nest in Maori burial caves, may use human bones as nest material.
Climate Vulnerability
Conservation Status
On some islands, where colonies had been nearly wiped out by feral pigs, shearwaters re-colonized after pigs were eradicated in 1936. Total population estimated at more than 2 million.