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Posted by Rosemary Drisdelle Jun 29, 2007 |
From May through September, Greater Shearwaters are seen off the eastern coast of North America, having migrated thousands of kilometres from their breeding grounds in the southern mid-Atlantic. They forage in coastal waters and on continental shelves all summer, putting on lots of weight so that they can complete the return journey to the Southern Hemisphere in the fall.
Sometimes the trip doesn’t go well and large numbers of the birds die along the migration route. Scientists aren’t sure why, but it probably often has to do with an inadequate food supply. With a migration route that keeps them traveling for months, Greater Shearwaters rely heavily on established foraging grounds. If there are not enough prey species at the foraging grounds—fish, crustaceans, and squid—some birds will die of starvation while on migration.
A die-off of Greater Shearwaters in mid-June 2007 resulted in thousands of dead and dying birds washing up on beaches in Florida and Georgia. Investigators suspect that starvation was the cause, although they routinely check for other things, such as mercury poisoning, and infectious agents such as bird flu.
With more than six million pairs of Greater Shearwaters breeding in the South Atlantic, a die-off of this magnitude is not likely to have much impact on the species as a whole, but it raises the question of what will happen if the predicted complete collapse of the fisheries comes to pass.
Read more about Greater Shearwaters:
Sources:
Meenan, Kyle. “Dead Migratory Birds Washing Ashore.” First Coast News 6/21/2007.