Tropical Storm Isaias passed last Tuesday, delivering us a glancing blow on its way through western Massachusetts and New York. We saw big gusts, spotty outages, and not nearly enough rain. But for the astute and ambitious birder, the storm brought gifts as well, gifts hoovered up from Caribbean waters and deposited far from home - Sooty Terns made a series of appearances in the region, delighting some lucky birders who picked up a life bird normally requiring a trip to a remote tropical island.
Many fans of the “hurricane birding” subgenre studied the predicted track of the storm and made plans accordingly. Past storms with similar tracks had deposited epic numbers of tropical waifs across a broad area. Would this be like Bertha from 1996, or more like last year’s Dorian? After stalling off Florida, the track stayed inland, eventually depositing tropical seabirds far inland on lakes in Berkshire County and Central Mass, where birders heavily armed with cameras waited.
Locally, single Sooty Terns were seen at Tuckernuck and in Buzzard’s Bay from both Marion and Bourne. Two were seen off Cuttyhunk and up to three at Race Point in Provincetown, where at least 10 birders saw and photographed them fishing the rips of the race among the other terns. Another was apparently seen off Monomoy a few days after the storm. While Sooties were the primary species displaced by Isaias, another tropical refugee, a Brown Booby, was seen off Woods Hole after the storm.
Sooty Terns are handsome, relatively robust tropical terns. Seen well, their back and wings are a soft velvet-black, such that Elvis would look right at home painted there. A black cap sets off their white forehead and underparts. Like most terns, the tail is graceful, long, and forked. But they are different from our terns in one important, peculiar way. They like being wet about as much as a cat does.
Sooty Terns are a paradox of a seabird. Though they rarely come to land over the course of their long lives, and are almost never seen resting, their plumage is not particularly waterproof - they would quickly become water logged underwater. While our local terns plunge into the water after bait fish as a way of life, Sooty Terns spend their lives at sea trying to avoid the sea. Like swifts and swallows, they mostly spend their lives aloft, only occasionally alighting on a piece of drifting flotsam or a surfacing sea turtle. To avoid getting wet, they pluck fish and squid from the surface or even the air, often depending large predatory fish like tuna to push the bait up and out of the water for them.
In fact, plummeting numbers of Sooties at some big colonies have been linked with the 60-80% decline in some tuna populations globally. The idea is that with fewer tuna to push bait to the surface, the adults are bringing lower quality prey like crustaceans and even grasshoppers to feed their chicks. Researchers discovered this by collecting tern vomit, to put it scientifically, along with fancier, more scientific sounding methods like stable isotope analysis.
I suspect you’re out of luck for finding your own Sooties – the storm is long gone and most likely so are the birds. But if you really want to see one, maybe you could volunteer for one of those research projects in the breeding colonies. Just think of it – working on a tropical island, all turquoise lagoons, sugar sand, and warm breezes. In fact, you may be in luck - I hear their last tern vomit collector just quit…