Migratory bird populations affected by hurricanes
By B. Blair Dedrick
Washington - On the morning after Hurricane Katrina, Judith Toups
woke up to see more than 30 ruby-throated hummingbirds in her
Gulf Port, Miss., backyard.
The hummingbirds were looking for food before their long migration
to the tropics. What they found instead were trees stripped of their
leaves, flowerless plants and few insects.
"The storm knocked out all the flowers," said Toups, a 75-year-old
founding member of the Mississippi Coast chapter of the Audubon
Society. "The food supply was pretty low."
Toups was not alone in her concern about the bird population after
Hurricanes Katrina and Rita. While the exact impact on the migrants
is unknown, experts say migrating bird populations will feel the
effects both this fall and into next spring.
Trans-Gulf birds, or birds that migrate across the Gulf of Mexico,
have at least a 550-mile, open-water flight from the Mississippi,
Alabama and Louisiana Gulf coastal regions to their Central and
South American winter homes. Other migrants take an overland route
via Texas and Mexico. Peak migrating season is from September through December.
In either case, the Gulf Coast is a major energy-building stopover
for the birds, who feed heavily before the long flight. The ruby-throated
hummingbird, for instance, doubles its weight before flying to wintering
grounds in Central America.
"The long-lasting and extensive impact of the hurricanes is on the habitat
that the birds use as stopovers," said Sidney Gauthreaux, a professor of
biology at Clemson University. "That effect can go over this migration
season and into the spring migration."
Gauthreaux uses Doppler radar, including that of the National Weather
Service, and thermal heat imaging to survey migrant birds. While
conditions on the Gulf Coast have prevented him from using his portable
gear to survey this season, he said he is concerned about the effect
the hurricane-ravaged habitat will have on the birds.
Normally, nearly 80 percent of migrating birds die during migration,
Gauthreaux said. That number can increase when winds and floodwaters,
or any other extreme factors, leave little to eat for the herbivorous
insects, like caterpillars, that most migrants eat. Berry-eating birds
are also in trouble, as the influx of salt water has probably killed
bushes that survived the actual hurricanes.
"It's a risky business," Gauthreaux said. "You don't know if the habitat
will be the way it was last year."
Bruce Reid is the deputy state director of Audubon Mississippi and head
of the Vicksburg, Miss., Bird Conservation Office. In addition to the
trans-Gulf migrants, Reid is concerned about migrant birds from Canada
that over-winter on the Gulf Coast.
"Frankly, one would imagine that a lot perished," he said. "And the only
ones who are left will have a harder time."
Watching out her windows, Toups said the number and variety of migrant
birds was extremely low at her house, about a mile from the beach where
some of the strongest winds and highest storm surges were recorded.
“Normally, we get almost anything, especially the insect eaters and wood-warblers,"
she said. "They are just plain not here."
Scott Sillet of the Smithsonian Institution's Migratory Bird Center said that
was not necessarily unusual under the circumstances.
"Migrants move along broad areas of the Gulf Coast," he said, explaining that
the birds fly with the prevailing winds.
Many birds will not stop if there is no habitat, Sillett said. The coastal
woodlands are a very important refueling stop for the migratory birds, and
most of those woodlands were destroyed.
Though the situation is not ideal, the area is slowly recovering, said Toups,
who has written a book and several articles about migrating coastal birds.
On the Mississippi coast, she has seen pear trees and other flowering plants
beginning to bloom as if in spring, and the hummingbirds are beginning to
thin out as they continue on their fall migration.
"Every day things get a little bit better," she said. "That's why I'm paying
attention. I want to see how long it takes backyard birds to recover and the
migrant birds to come back."
Source: Scripps Howard Foundation
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