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Saturday, September 1, 2012

How do birds deal with hurricanes?

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.

 So let’s keep Louisiana and areas north of it on our minds and in our thoughts. It certainly could have been a lot worse. The birds might have an interesting few weeks as well.

 


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.
 

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