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Continued from The Loon or Diver in Flight, Diving and on the Water
Food
Loons or Divers eat small or medium sized fish, which they capture
and usually even swallow under water. Usually it is only rare that different
types of food provide supplementary nutrition. This can be frogs,
crustaceans, worms, molluscs, or water insects. There are however cases,
in which Loons breed at lakes which are completely devoid of fish-free,
and then occasionally their diet completely changes over to molluscs or
insects.
Their prey is located by sight and is for this
reason that they prefer to hunt in clear waters. For the same reason
they do not hunt at night. All their prey must be alive at the time
of being caught. They do not seem to like eating dead animals, which
makes it slightly difficult to keep loons in captivity, especially where
they are in rehabilitation centres after being found wounded or sick.
Loons have a very flexible esophagus, which makes
it possible for them to swallow relatively large prey. The Common Loon
can swallow heavy trout or even flounders up to 45 centimeters in length
and a kilogram in weight. Swallowing large prey animals can, however, fail
in very rare cases, and Loons have been found who have suffocated on large
fish.
Statistics carried out have estimated a consumption
of fish equal to approximately one ton over the breeding season (which
lasts around 120 days) for one pair of loons with two chicks. Other estimates
say about one ton over a full year. Whichever it may be, this is
a strong demand for food due to their remarkable expenditure of energy,
which is increased by the aquatic and cold habitat in which they live.
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Habitat
Loons or Divers inhabit northern areas comprising
the tundra and taiga habitats of Cananda, Greenland, Russa, Scandinavia
and Greenland. Two species, these being the Black-throated Diver
(also known as the Arctic Loon) and the Red-throated Diver
(Red-throated Loon) breed in Northern Europe. The Southernmost
areas for these two species to breed is in the North of Ireland, Northern
Scotland as well as the South of Sweden and Norway. The Common
Loon (known also as the Great Northern Diver) breeds in North
America in particular, as well as in Iceland and Greenland. The Yellow
Billed Loon (also known as the White Billed Diver) inhabits
the Northeast of Siberia and North America.
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Loons or Divers spend their entire life on, or
very close to, the water. The breeding areas of the larger species
are in deep lakes of the tundras and boreal zones. A quiet habitat
free of disturbance is preferred. The Red-throated Loon, being the
smallest of the 5 species, also breeds in small lakes and ponds. If the
possibility exists, small islands within the lakes are preferred as nesting
places. In rare cases, Red-throated Loons and yellow billed Loons alse
breed also in protected sea bays or river deltas.
Loon Migration
In winter the Loons or Divers migrate to the coasts
of Europe, Asia and North America. The European populations they
winter around the Baltic Sea as well as the northern Mediterranean. In
North America they fly southward to Northern and Florida. In Asia
they inhabit the Chinese coast down to Hainan.
The Greenland and Icelandic populations of the
the Common Loon can be observed in the Winter on European coasts.
More populous however are Red-throated Loons and Arctic Loons and who also migrate in the winter
to Central European coasts. Particularly on the autumn stretch of their
migration both Arctic Loons and Red throated Loons rest either individually
or in small flocks deep inland in Central Europe, usually on large lakes.
In particular the North Siberian populations of the Arctic Loon exhibit
thereby a particularly interesting migration course behavior. In the autumn
they move to the black sea, in spring their migrations take them first
to the Baltic Sea and from there out to the white sea. Such a migration
route, which the birds use in the other direction on their return journeys
to the breeding areas in the autumn, is called loop migration and
is, so far as is known, only used be a few types of bird.
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