Page 380 - (DK) Ocean - The Definitive Visual Guide

378 ANIMAL LIFE

Birds MURRE DIVING
Using their wings as hydrofoils, common
murres speed through icy water in search
of fish. Members of the auk family, they
BIRDS THAT HAVE ADAPTED to life at sea are common in northern seas.
DOMAIN Eucarya
spend their lives in the air above the surface,
KINGDOM Animalia
in the upper layers of the open ocean, or
PHYLUM Chordata
along shorelines. Shore- (littoral) based birds
CLASS Aves
rarely range far from land, and some visit the
ORDERS 29
coast only at certain times of year. Others
SPECIES 9,500
are pelagic, often remaining at sea for
months on end and returning to land only to breed. Unlike land
birds, many pelagic sea birds breed in large colonies on islands
and cliffs, deserting them when the breeding season ends.

Anatomy
There is no such thing as a typical sea bird, although pelagic birds share many
adaptations for life at sea. These include webbed feet, highly waterproof plumage, and
glands that get rid of excess salt. Most terrestrial birds have hollow, air-filled bones
(an adaptation that helps to save weight), but in diving species, such as penguins,
the bones are denser and the air spaces reduced.
Some plunge-divers, including gannets and pelicans, have air sacs under their
skin. These cushion the impact as they hit the water and help them to bob back
to the surface with their prey. Compared to these marine species, shoreline birds
show few specific adaptations for life in or near salt water but, like all birds, they
have bills specialized for dealing with different kinds of food.
streamlined bill
FLYING DIVER
narrow wings ideal for
long-distance flight The northern gannet’s streamlined shape
is typical of a plunge diver. Its nostrils
open inside its bill, enabling it to keep
out water when it hits the surface.

webbed feet
tubular, external
food pouch nostril
BILL ADAPTATIONS
Apart from waterfowl, most
birds of the sea and shore are hooked tip
carnivores, with bills that are
adapted for different kinds of long bill can
animal prey. A pelican’s bill and PELICAN ALBATROSS probe deep into
pouch work like a scoop, while estuarine mud
an albatross’s hooked bill can grip hooked bill
slippery prey, such as jellyfish. Sea
eagles catch their prey with their
talons, but then use their bills to
tear it into pieces. Curlews have
long bills that can probe for
animals buried in mud.
SEA EAGLE CURLEW
Habitats
Birds live throughout the world’s oceans and shorelines, from the
equator to the poles. Less than 200 species are truly pelagic, meaning
that they ply the oceans. These oceanic birds include albatrosses, which
have wingspans of up to 11 ft (3.5 m), and much smaller species, such
as shearwaters and terns. Although they feed on sea animals, their true
habitat is the air: the sooty tern, for example, hardly ever rests on the
water and may spend its first five years entirely on the wing.
However, food is widely scattered in the open oceans, which COASTAL WADERS
OCEAN LIFE continental shelves, while rocky coasts and mudflats are key OCEAN WANDERER Eurasian oystercatchers feed in
is why the majority of sea birds live closer to land.
Most diving sea birds feed in the shallow waters over
a variety of coastal habitats, from
The black-browed
habitats for waders and gulls. Estuaries are important habitats
rocky shores to mudflats. These
albatross travels long
for coastal birds. Their muddy silt often harbors numerous
birds are waiting for the tide to
distances in search of
worms and mollusks, accessible at low tide. In the tropics,
turn so that they can start to feed.
good feeding grounds. Its
mangrove swamps attract birds for the same reason; they also
diet includes crustaceans,
have the added bonus of trees, in which birds nest and roost.
fish, squid, and carrion.