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Continued from Food, Habitat and Migration of the Loon or Diver
Call of the Loon
The characteristic call of the Diver or Loon is an
extremely loud and melodious howling, which carries far and is one of the
loudest calls, which are to be heard in the arctic expanses. It is also
said to be the most disquieting sound to be heard in these places of otherwise
relative silence. This cry only occurs during the breeding season,
and serves to demarcate the bird's territory. In the the Red-throated
Diver or Red-throated Loon, both partners call. In the
other 4 species, only the males utter these calls. This howling is
a different sound to a separate call that the loon uses when in danger.
For example, in the White Billed Diver which is also known as the
Yellow
Billed Loon, this danger call sounds like a screeching laugh.
Occasionally they will call out whilst in flight.
Breeding and Chicks
Loons live in Monogamous pairs. They return annually
at the breeding season to their previous year's breeding grounds, and also
remain together during their migration and in their wintering grounds.
They do not produce young in every year - approximately every fourth year
the pairs do not produce a brood. A complex mating ritual does not
occur in Loons. New couples use a number of synchronous movements on the
water including rapid dips of the dipping their bill, diving and swimming
underwater. With older pairs these few ritual behaviors are even less.
Mating occurs on the waterbanks. Often the mating
begins right after the birds have arrived in the breeding area, and continues
over the next days. If it always occurs at the same place, a hollow in
the soil can develop thereby, which is often then later used as the nest.
The nest itself is built from aquatic plants and Mosses and is around 4
to 10 centimeters high with one small depression in the center. Nearly
all of the building material is collected by the male. The nest is
always on the waterbank or nearby, hardly ever any further than a meter
from the water.
One to three eggs are laid, with two being the
usual number. The eggs are a tawny-olive colour with dark spots.
Both parents incubate the eggs. After hatching, the chicks remain
in the nest for about three days before they go into the water. Even at
this young age they are already swimming and diving. Often they also
rest on the backs of their parents. Up to the age of seven weeks,
and sometimes beyond, the chicks are fed by their parents. At an
early stage, one of the young birds proves itself to be the strongest and
gets hold of the most most food for itself. If no plentiful food supply
is present, this often results in the death of the weaker chick.
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The chicks are independent after 7 weeks in the
case of the Red-throated Loon, and 9 weeks in the case of the other 4 species.
After this period, the chicks are still sometimes fed by the parents, but
very irregularly and only whilst they remain in the area around the nest.
Once they have attained full growth, Loons have
few enemies; only large birds of prey such as sea-eagles can occasionally
carry off a Loon. Young birds sometimes fall victim to ravens and crows,
seagulls, Skua, Otters or large fish.
The knowledge for the lifespan of the individual
species is so far incomplete. Arctic Loons and Red Throated Loons reach
ages of over ten and sometimes even over twenty years. With an Arctic Loon
an age of 28 years was was proven. However until now (the year 2006) no
specimen of the Common Loon which would have reached an age of more than
eight years is known. This is however surely not the actual maximum
age.
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In territorial behavior the Red-throated Loon differs
from the larger species. The latter are territorial and defend their territories
aggressively against all intruders. On the other hand the nests of the
Red-throated Loon often lie closely together, and only the direct area
surrounding the nest is defended. Most of the time, a threatening
posture serves as enough to to turn away an intruder. Things rarely come
to a fight, but if they do, it can be extremely violently and can end with
the death of an adversary by drowning or blows from the bill.
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