Major storms like hurricane Isaac are unquestionably harmful in many ways. They've been occuring for ages; and will certainly occur again. As of this writing, Isaac has done its worst, and is slowly fading away. But more hurricanes WILL occur. So I will not stray from the core purpose of this blog. Hurricanes are interesting, recurring events with regard to birds and migration.
As you might imagine, many birds fly rapidly from
the area as a hurricane approaches. They’re alerted by the sudden drop in
barometric pressure which they instinctively know means “leave fast”. After
all, birds have been dealing with storms for ages. A few will choose
to stay put if they can find shelter, and ride it out.
In addition to the drastic pressure change,
hurricanes approach from the south. They’re huge storms,
with counterclockwise winds, carrying lots of water. This means that ahead
of the core of the storm, winds will be blowing essentially from
east to west.
At the same time, our fall-migrating birds are
heading from north to south, many down the Central Flyway (which includes north Texas), and will be driven farther west into Texas. This will obviously increase the concentration of migrating
birds coming through north Texas, and decrease the number of birds moving
through the east side of the storm. As the storm approaches,
winds will be strong, and birds would probably not brave
headwinds in excess of 100mph just to follow their usual migration route. The south winds are far more destructive than east-to-west winds.
So east Texas should be spared from significant wind damage by a storm that hits Louisiana.
The non-migrating birds in the path of a hurricane
just hunker down in a crack in some rocks, under the eave of a house or in a hole in a large tree. Some, unfortunately, will be killed. Others may get
blown far away by a big storm (Katrina blew many birds as far away as
Tennessee).
While watching migrating birds may be good in Texas
this week and slow in Florida, another group of birds may visit. These are the
water/shore birds (“pelagic” species) that live along coastlines. Many of them
get "trapped" in the eye of the hurricane and carried well inland, to
places and habitats they haven't a clue about. Naturally, they turn around and
head back to the coast as soon as they can. But it’s not out of the question
that someone will see, for instance, a Shearwater or Avocet in north Texas as
the remnants of a hurricane pass through. Pelagic birds often drop from
what’s remaining of the hurricane’s “eye”, into large lakes.
Of course, the biggest threat to all kinds of birds
is the loss of habitat. Despite the fact that a hurricane loses strength over land, it can still harm birds. A Cardinal who lived in an Arkansas forest, for
example, may have his forest blown down. Or a Meadowlark may suddenly have his
meadow underwater. Or a Woodpecker in a Louisiana swamp may have his habitat
inundated by salt water from the gulf. This affects both the birds’ homes and
their food supply.
A U.S. federal court has ordered the Federal Communications Commission (FCC) to protect migrating birds from colliding with commucation towers (cell phone, television, generation etc.). Each year between 5- and 50-million migrating birds (and many bats) are killed by such collissions. Companies now applying for tower permits must comply with existing federal regulations protecting birds.