How Do Hurricanes Affect Birds?
When severe weather hits, humans hunker down. But what about the feathered among us?
Birding expert and Audubon field editor Kenn Kaufman's interest in hurricanes began 35 years ago, when he covered the effects of Hurricane Kathleen, a storm that brought droves of seabirds into the American Southwest, for American Birds. As this year's hurricane season winds down, he shares some of the insight he's gained over the decades.
How do hurricanes affect bird migration?
Any day in late August, September, or October, vast numbers of little birds are heading southward during hurricane season. When they fly into one of these systems they have no way of detecting what's ahead.
You've probably heard about the radio-tagged whimbrel story: The bird flew through the recent storm Irene and made it out the other side. They're pretty tough birds--one of the larger shorebirds. I'd doubt that little warblers and thrushes could do that. There are probably substantial numbers of little migrants that just get taken out during the storm. Storms can also drop a lot of exhausted birds back to some point that presumably they'd left a day or two before.
How do birds travel with a storm?
The birds get into the end of the hurricane's spiral and they move toward the eye of the hurricane. They may not necessarily do that in any organized way; more likely they're out there in all this wild wind and when they chance into the calm of the eye they may make an effort to stay there and travel with it rather than fighting the winds again.
When the storm reaches land, some of them may start fighting the winds. Others may go with it and travel with the eye until the hurricane dissipates. The majority of seabirds, if they are not too weakened from having flown for so long without food, will probably find their way back to shore quickly. They have great powers of navigation.
Do birds have any specialized response to hurricanes?
Presumably a bird tends to take off when the wind is favorable, just after the passage of a low-pressure system. Because regular airflow of a hurricane moves counterclockwise, after the system passes to the east, there may be winds from the northwest. The birds will take off with that. If they take off when conditions are good, there's a chance that they're not going to run into a hurricane.
Why do some birders chase hurricanes?
First, I need to point out that for people to deliberately put themselves in harm's way, in a hurricane's path, they have to be totally crazy.
That said, a bunch of my friends have done just that. With Hurricane Irene, some friends of mine were out at dawn the next day and saw all kinds of tropical seabirds, like bridled terns, sooty terns, and brown noddies.
I think the big deal about Irene was all of the white-tailed tropicbirds that were carried up along the coast and even inland. These are strictly offshore birds--they nest in the Caribbean.
Today we know that if you are far enough offshore or in the Gulf Stream, you'll see black-capped petrels regularly. But 50 years ago most records of black-capped petrels were sighted after hurricanes. At one time, if you wanted to see a black-capped petrel, you just prayed for a hurricane.
What happens to a bird's habitat after a hurricane?
Changes in habitat are going to change the composition of bird life in a given spot. I remember reading about an area in New England where a bunch of hurricanes knocked out most of the trees in 1938, but afterward, the density of breeding birds went up. It opened up the area and birds that favor second-growth and openings, such as mourning warblers, came in and occupied the new spaces.
There are always winners and losers when habitat changes.