Two years ago Hurricane Harvey roared onto the Texas coast leaving behind death and devastation. It ravaged cities and countryside, including the Aransas National Wildlife Refuge where the rare Whooping Cranes spend the winter. Another particularly vulnerable species, the seaside sparrow, may have been eradicated from the area, as its habitat
was flattened and flooded. We know birds must lose their lives in these sorts of storms, but the longer term damage to habitat is equally deadly. This is a classic example of how a catastrophic weather event can impact a species that is already dwindling in population. Ground nesting birds, water and wading birds all suffer from these types of storms. As for the Whooping Cranes, according to the International Crane Foundation, their habitat remains healthy and ready to welcome them back this fall.
It’s a different story in the Bahama Islands. Now we have seen the horror of a direct hit by a Category 5 hurricane on islands far from the mainland. The devastation on Grand Bahama and Abacos islands looks complete – no houses or trees standing. The human loss is devastating and the numbers of dead will continue to rise. Our hearts go out to the people of this island nation and aid will be sent from around the world.
What we don’t see is the desperate situation for wildlife. It would seem that of all the wild creatures, birds would have the greatest chance of survival because they have wings to carry them away from the dangerous storms. They may sense changes in barometric pressure and this can affect behavior, but many times they are caught nevertheless in the crosswinds and rain and storm surges.
Hurricane Dorian may have caused the extinction of one very rare bird species. The Bahama Nuthatch was already
reduced to possibly one or two individuals. They were only found on Grand Bahama Island and their numbers had been reduced over time by logging of the Caribbean pine forests they depend on for food and nesting. In a 2004 survey there were an estimated 1,800 individuals. Besides the logging, habitat destruction and damage came from tourist developments, and previous hurricane damage.
Other threatened endemic birds in the Bahamas include the Bahama Swallow, Bahama Warbler and Bahama Yellowthroat. The Bahama Parrot, also known as the Abaco Parrot lives on several of the islands that were directly hit by Hurricane Dorian. In an especially sad twist of fate, the birds have been making a recovery in numbers due to the establishment of parks and control of feral cats. In 2008, the parrots’ estimated population was roughly 5,100, and by 2016 it had expanded to an estimated 8,800 – a nearly 60% increase. All of these birds had to somehow survive the extremely high winds, torrential rainfall and flooding.
Hurricane season unfortunately coincides with the migration season for millions of birds. Many of the migrants on the East Coast of the U.S. follow a path that takes them over or to the Caribbean islands, including the Bahamas. These act like stepping stones on their way to South America. If they were not caught in the storm and are still traveling south, they will find little to no food when they arrive on some of these islands. If any trees managed to stay upright, they have had their fruit or vegetation stripped from their branches and this is where migrants would find food like insects or fruiting fall flowers. Some species specifically need leaf litter that is found on the ground under the trees, again because of the insects that hide there. With the amount of flooding the islands received, that food source is gone.
There is another consequence of hurricanes on birds. Some birds are actually caught inside the eye of the storm. This phenomenon is called “entrainment”. Most often it is seabirds that fly inside or rest on the water until the storm passes over land where they will try to take refuge. This is how some birds end up in locations where they are normally not found and why serious bird watchers often flock to these regions afterward. After Hurricane Dorian a pair of Brown Boobies was found for the first time on the coast of England, and several hundred Laughing Gulls ended up in Nova Scotia, likely taken all the way up from the Carolinas or Florida.
For those birds that survived, the short-term response before the original vegetation and invertebrate life recover will include shifts in diet, foraging sites or habitats, and changes in reproduction. How quickly a remnant population recovers will depend on their ability to find nesting sites and recruit others of their kind from undisturbed patches of habitat.
In the coming months and years scientists and others will see how the hurricane reshaped the islands and their vegetation. It will take longer to determine whether the threatened bird species are still with us or if Hurricane Dorian was their last unsurmountable challenge.
By Kate Crowley