Ocean
Watch
Monday, August 24, 1998
Local food entices
even first-season
plovers to isles
LAST week, during a beach walk at Ko Olina, I noticed a
golden plover. I watched the elegant bird high-step in the sand, wondering
if our plovers are back from Alaska now. Since some spend their summers in
Hawaii, seeing just one here and there doesn't mean much.
By the time I reached the end of the half-mile-long
path, I counted 13 plovers. Some were prancing, others were eating and two
were squabbling over territory.
Seeing this many plovers in such a short distance
confirmed my suspicion: Our favorite shorebirds are back for the winter.
Of all the subjects I write about, these migratory
birds, called kolea in Hawaiian, generate the most mail and calls. After
my column of May 18th, in which I described biologist Wally Johnson's
research with plovers, I received lots of interesting questions. Here are
a few.
Johnson and his colleagues have learned that adult
plovers leave their Alaska breeding grounds for Hawaii in August, but the
chicks don't go until October or November. How, then, one reader asks, do
the chicks know where to go?
Johnson replies that juvenile plovers (and the young of
many other birds) are genetically programmed to fly south. Their ultimate
destination, however, is a matter of chance. Since the Hawaiian
archipelago is a big target for birds coming from Alaska, many stop here.
STILL, that first migration is a time of high
mortality. Adults already in Hawaii compete with the young kolea that land
here. However, if juveniles are successful that first year, their chances
for continued survival are good.
Another reader told of a plover on her workplace lawn
that appears calm and minds its own business when she and other regular
workers walk past it. But when a stranger strolls by, the bird often
squawks and leaps aggressively. She wonders: Do these birds recognize
certain people?
Yes, says Johnson. Plovers can come to know certain
people through repeated contact. This is especially true if the person is
feeding them.
There is plenty of evidence that plovers are smart. In
one case, an injured bird learned to take food from a human hand in six
days. Also, once plovers have been caught and banded, they rarely get
captured again. Obviously, experienced birds remember situations to avoid.
Several readers reminded me that in the May column, I
didn't mention what kind of food plovers eat in Alaska.
IN Alaska and Siberia, the birds eat beetles, flies,
grubs, worms, snails, spiders, crustaceans and berries. In Hawaii, plovers
eat snails, weevils, skinks, moths, caterpillars, cockroaches, bees, ants,
flies, earwigs, earthworms, sowbugs, mites, millipedes, blind snakes,
geckos, flowers and leaves.
Another reader wonders why plovers go to Alaska at all.
Why not just stay in Hawaii and raise their young here?
One reason is that in prehistoric times, plovers didn't
have it so good in Hawaii. The land was thick with forests, and there were
less animals to eat.
Then, about 400 A.D., people began arriving, clearing
the land and importing large numbers of alien species. Thus, there is now
much more open space for plovers to forage in, and more here to eat, than
when these birds evolved their migration patterns.
Also, even though it seems like there's plenty of food
for plovers here, the supply is small compared to the far north.
During Arctic summers, the air and tundra are sometimes
so thick with insects, you inhale them as you walk.
It's fun having our plovers back, entertaining us with
their lively behavior. It's also fun reading your stories and answering
your questions about these birds. Please keep writing.
