Loon Magic/Loon Magic - Wayzata Technology (8011) (1993).iso/mac/mac text/02 Family - Arctic⁄Pacific

Text File | 1993-07-20 | 9KB | 156 lines

   A Family Portrait

   Arctic loon, Gavia arctica
   Pacific loon, Gavia pacifica

   Until recently, ornithologists have recognized four species of loons:
common, yellow-billed, arctic, and red-throated. Recent evidence
from Russian scientists, however, suggest that the birds we have
called arctic loons are really two speciesmthe arctic loon (Gavia
arctica) and the Pacific loon (Gavia pacifica). Based on this new
classification, all of the "arctic loons" in North America are really
Pacific loons. While little is known of the differences between these
species, one distinctive characteristic, apparent only during the
breeding season, is the color of the iridescent head feathers. The
arctic loon's head looks green while the Pacific loon's appears purple.

   The Pacific loon is probably not as closely related to the common
loon as the yellow-billed. However, the Pacific and common loons are
not so evolutionary divergent as to prevent occasional interbreeding.
Apparent hybridization between Pacific and common loons has been
reported at least twice in the scientific literature. In 1973, Ian
Robertson and Mark Fraker were conducting environmental studies
for the Gulf, Imperial, and Shell Oil Companies in Canada's Yukon
Territory. They observed a family of loons consisting of an adult
common loon, an adult Pacific loon and two chicks. Both adults were
in breeding plumage and gave calls appropriate for the respective
species. They watched the family for most of the summer. While they
had no scientific proof that the chicks were a common-Pacific cross,
there seemed to be little chance of any other possibility.

   Unlike the yellow-billed loon, the Pacific loon differs from the
common loon in many ways. Pacific loons breed throughout the
tundra and taiga regions of Alaska, the Yukon and Northwest
Territories. It is also found breeding in northeastern Saskatchewan,
northern Manitoba, northwestern Ontario, the Belcher Islands and
northwestern Quebec. When Ralph Palmes defined its breeding range
in 1962, Alberta and British Columbia were not included. E.O. Hohn
recorded a breeding Pacific loon in Alberta in the early 1970s and
more recently, the Pacific loon has been found nesting in two areas in
northern British Columbia. Two pairs of Pacific loons have been seen
nesting on subalpine lakes in west coastal British Columbia.

   Arctic loons nest across northern Europe and Asia including the
British Isles, Scandinavia and Russia. Like the other loons, arctic and
Pacific loons winter primarily in coastal areas. Arctics can be found
as far south as Spain in the northeastern Atlantic and also occupy the
Mediterranean, Black, Caspian and Aral Seas. Arctic loons nesting in
Siberia probably are the ones wintering in the eastern Pacific from
northern Russia south to China.

   Pacific loons winter off the North American Pacific Coast from
northern Sonora, Mexico to southern Alaska. Pacific loons are seen in
small numbers, but frequently on freshwater lakes and reservoirs in
southern California, Arizona and New Mexico. Each year, at least one
Pacific loon seems to show up in Duluth-Superior harbor to spend
part or all of the winter in western Lake Superior. Apparently some
Pacific loons like U.S. coastal waters. American Birds magazine
contains a report of 200 Pacific loons spending most of the summer
near the south jetty of the Columbia River in Oregon.

   Arctic and Pacific loons nest on lakes that receive relatively little
human disturbance over most of their breeding range. In a few areas
they share their nesting lakes with people. Graham Bundy found
arctic loons successfully raising young on lochs in northwestern
Scotland frequented by fishermen. In the city of Anchorage, Alaska
nongame wildlife biologists from the Alaska Department of Fish and
Game have reported Pacific loons nesting within the city limits,
making Anchorage the largest city in North America with nesting
loons.

   Like the other loon species, Pacific loons apparently are unable to
recognize their own young from another loon's chicks. One pair of
Pacific loons in Alaska really had a case of misidentification. Kenneth
Abraham, a summer employee of the U.S. Fish and Wildlife Service,
observed a mated pair of Pacific loons tending a brood of five
spectacled eider ducklings.

   The loons and a pair of eiders had nested only ten meters apart on
a small island in the lake. Abraham did not see what happened to the
adult eiders or the loon eggs. After watching both pairs incubate
their own eggs, he was surprised to find the eider ducklings tended
by the Pacific loon adults. The loons and the ducklings accepted each
other well. The loons protected the ducklings from predatory gulls
and even let the ducklings ride on their backs. Although eider
ducklings are capable of catching their own invertebrate meals, they
were happy to accept free handouts from their "adopted" parents.
Pacific loons typically catch and feed the same kind of aquatic insects
that eider ducklings catch on their own.

   Arctic loons have been studied extensively in Europe and Pacific
loons have received a fair amount of research attention in North
America. Two studies in particular established much of the baseline
data on the ecology of Pacific loons. From 1967 to 1969 Rolph Davis
studied Pacific and red-throated loons on the western coastal plain of
Hudson Bay in the Northwest Territories as part of his Ph.D. program
at Western Ontario University. In 1974 and 1975 Margaret Petersen,
then a Master's student at the University of California-Davis, studied
Pacific and red-throated loons near the Bering Sea in western Alaska.

   These two studies did not reveal anything about the nesting
ecology of Pacific loons strikingly different from that of common
loons. In fact, it was the similarities that were striking. Although
smaller than the common loon and nesting on more northern lakes,
the Pacific loon seems to be a close counterpart of the common loon.
Like the common loon it lays two eggs, incubates the eggs for
twenty-eight to thirty days and raises the young on the nesting lake,
obtaining all of the food for the chicks from the nesting lake. Thus,
except for the obvious physical differences and some different calls,
Pacific and common loons are quite similar.

   Pacific loons and red-throated loons occasionally share the same
lakes, but red-throated loons are careful to keep their distance from
the larger and more aggressive Pacifics. Maybe red-throated loons
know something that a Canada goose found out the hard way.

   Two of Rolph Davis' student colleagues at Western Ontario
University were studying Canada geese in the same areas as Davis'
loon study. One day in June, 1967 they observed an aggressive
encounter between a male Canada goose and a Pacific loon that left
the goose dead. Inspection of the dead bird revealed a 6-inch deep
puncture wound in the chest that struck the pulmonary artery and
the wing. They guessed that the loon must have sunk the entire
length of its bill into the goose's breast.

   Nineteen sixty-seven must have been the year to watch Pacific
loons. That year Maston McNicholl, now the director of the Long Point
Bird Observatory in Ontario and the Ontario Lakes Loon Survey,
observed some strange behavior of a pair of Pacific loons. While
checking nearby nests of arctic terns and herring gulls, McNicholl
noticed a Pacific loon nest unattended by either adult. From time to
time he did see a Pacific loon flying over the lake apparently
"checking" the unattended eggs in the nest. This happened almost
always on calm days. McNicholl suspected that the adults were
feeding in nearby Hudson Bay (about a third of a mile away) and
were doing so only on calm days which are preferred for feeding. He
explained their behavior by hypothesizing that it may have been
advantageous for both adults to feed providing that the eggs were
"checked" periodically to deter potential predators. The "checking"
behavior may have resulted from a conflict between the urges to
feed and incubate the eggs.

   Except for its alarm call, which is very similar to a common's
tremolo, the vocalizations of the Pacific loon are unique. They are
usually described as guttural with a wide range of wails, shrieks,
squeals and yelps. After listening to Pacific loons for several months
in Alaska, one researcher compared their call to the bark of a dog,
while another compares the call to the cackle of a hen. When
disturbed, the Pacific loons can emit a high pitched squeal. According
to Gabrielson and Lincoln, Pacific loons on their breeding grounds are
"among the noisiest of all waterfowl." They quote one naturalist who
found the wail heart-breaking and added, "if ever a species enjoyed
spreading sorrow through the bird world it is this loon." Looking at
the dramatic breeding plumage of the Pacific loon, it is difficult to
relate such beauty with sorrow. Probably to other Pacific loons the
vocalizations are sweet music - it's all in the ear of the listener.