With all the recent attention on Hurricanes Fay and Gustav, many people are wondering about the effects of hurricanes and tropical storms on birds. While numbers are hard to come by, it is clear that a lot of birds are killed outright by hurricanes. This is especially true of seabirds, which have nowhere in which to seek shelter from these storms. Beaches may be littered with seabird carcasses following major storm events. Most Atlantic hurricanes occur in late summer and early fall. Fall storms coincide with bird migration and may disrupt migration patterns severely. Many birds get caught up in storm systems and blown far off course, often landing in inhospitable places or simply arriving too battered and weakened to survive. Others, while not killed or displaced by storms, may starve to death because they are unable to forage while the weather is poor. The number of birds that die as a result of a major hurricane event may run into the hundreds of thousands.
Healthy bird populations are able to withstand such losses and have done so for eons. However, hurricanes can have severe impacts on endangered species, many of which occur on tropical islands, often among the places hardest hit by hurricanes. For example, Hurricane Hugo in 1989 killed half of the wild Puerto Rican Parrots existing at that time. The Cozumel Thrasher, found only on Mexico's Isla Cozumel, was pushed to the edge of extinction by Hurricane Gilbert in 1988. Hurricane Iniki may have wiped out the last survivors of as many as three bird species when it hit Hawaii in 1992.
Apart from the direct, physical effects hurricanes may have on birds, they also can have detrimental effects on bird habitats. Cavity-nesting species can be especially hard hit because the trees in which they nest often are blown down or snapped off at the cavity. Hurricane Hugo, which hit the Carolinas in 1989, destroyed most of the area's nest trees of the endangered Red-cockaded Woodpecker; one forest lost 87 percent of its nest trees and 67 percent of its woodpeckers. Only through the installation of artificial nest boxes have these populations been restored to pre-storm levels.
Although birds blown out of their normal haunts by storms often don't survive, bird-watchers by the hundreds may flock to see them. Usually, such sightings involve seabirds blown inland and appearing on lakes and reservoirs. First state records of many species have been obtained in this way. Some birders even head into hurricanes to see lost birds.* Others raptly study weather maps to try to predict where hurricane-swept birds will wind up. Recently, during Isabel, birders were staked out in an organized fashion around New York's Cayuga Lake to see what showed up. Land birds blown out to sea typically perish unnoticed.
It's important to remember that the long-term effects of hurricanes on birds aren't necessarily negative. Every disturbance event is bad for some species but good for others. For instance, hurricanes create gaps in forests, creating habitat for species that require a brushy understory. Birds blown off course occasionally establish entirely new populations; such events may be responsible for much, if not most, colonization of remote islands by birds. Furthermore, hurricanes have been around for a long time and are part of the system in which birds evolved. It is only when they have impacts on species already pushed to the brink by humans, or if hurricane activity is increased by global climate change, that there is cause for concern.
*Epitaph for a hurricane-chasing birder (not original):
Here he lies
A little wet
But he got
His lifelist met.