Thursday, December 30, 2010

Birdland: Sooty Terns

A Sooty Tern on Tern Island, French Frigate Shoals, Northwest Hawaiian Islands
(Source: U.S. FWS @ Wikipedia)

"The air was filled with birds screaming very loudly..."

Thus wrote J.M. Brooke of the USS Fenimore Cooper while surveying Johnston Island in the Pacific in March 1859. It is not clear to me what the Fenimore Cooper was doing at Johnston at that time. During the same year, the ship came across French Frigate Shoals (home to the sooty tern pictured above) and members of the ship attempted to claim U.S. sovereignty over the shoals under the 1856 Guano Islands Act. They could do so, they reasoned, because the shoals were uninhabited (by humans, not birds) and contained an estimated 25,000 tons of guano. Unfortunately, two minor details confounded their plan: one, the Guano Islands Act only granted private individuals/corporations the right to claim guano islands as U.S. possessions, thus the law did not cover the claims of persons representing the U.S. Navy; and two, French Frigate Shoals actually had nowhere near 25,000 tons of guano. And whatever they did have was not profitable enough to mine.

That was good news for the Sooty Terns. Yet things wouldn't turn out so well for the Sooties on Johnston Island. Guano mining may have had some effect on them in the 1850s and 60s, but military build-up and weapons stockpiling (and dumping) in the mid-twentieth century most definitely affected their ability to breed. According to one account, by the 1950s the Sooty Terns had been all but extirpated from Johnston Island. (As of 1975 they still had not returned; I'm not sure about the situation today.) But they did keep breeding - in enormous numbers - on Sand Island, a nearby island within Johnston Atoll.

Another Sooty Tern at Tern Island, French Frigate Shoals
(Source: U.S. FWS @ Wikipedia)

What are Sooty Terns?
Well, those who prefer Latin names knew them for centuries as Sterna fuscata. But within the past few decades their genus has been changed to Onychoprion; thus, Onychoprion fuscata. The change is a bit confusing, as Sterna and Onychoprion both commonly mean "terns."
The Rapa Nui call them manutara; manu means "bird"; tara apparently means "tern." You can read my earlier discussion of the importance of manutara (Sooty Terns) in Rapa Nui history in my earlier post about the 1994 film Rapa Nui.
Manu also means "bird" in the Hawaiian language. But Hawaiians have a more specific name for the Sooty Tern: ʻewaʻewa. One online source suggests that the name ʻewaʻewa refers to the "cacophony" (ʻewa: "crooked, out of shape, imperfect") of sound that the birds habitually make. (Remember Brooke wrote in 1859 that "the air was filled with birds screaming very loudly..."!) But ʻewaʻewa can also mean "biased," or "unjust." Might this name describe a certain behavioral or personality trait of the sooties?

But let's move beyond names. In truth, names tell us a lot more about the humans doing the naming rather than about the birds that are being named.
Sooty Terns breed on islands all across the tropics, from the Pacific to the Atlantic to the Indian Oceans. Their feeding range is "pan-tropical": between the Tropic of Cancer and the Tropic of Capricorn. Like many seabirds, Sooty Terns spend most of their lives flying across the ocean, looking for food, even sleeping on the wing. Islands only matter to them as places to breed, and that is because their eggs need a place to hatch. (You can't raise chicks in the air or on the water!)

A Sooty Tern egg
(Source: Wikipedia)

So what is life like for a Sooty Tern chick on a Pacific Island? Well, on Johnston Atoll in the 1960s, for example, you probably popped out of your mommy in March. Your first taste of the outside world was from within your egg. You were not laid in a nest, nor even in a bush or a hole or on a tree. You were very likely laid right on the ground. Sooty Terns are somewhat unique in their disregard for where they lay their eggs. This habit is partly the consequence of millions of years of evolution within Pacific Island environments where there were absolutely no mammalian predators. So you can imagine what happened in the 1800s when some of these islands became infested with rats...rats that love eating chicks...and eggs.

Human guests of the Sooties had their own theories for why these terns laid their eggs directly on the ground. Dr. Thomas H. Streets, U.S. Navy, derisively said of the Sooty Terns on Palmyra Island in 1877 that their eggs "are dropped apparently anywhere..." That wasn't a very generous comment. Richard Branscombe Chave, an employee of a guano company who got himself stranded on an uninhabited coral atoll in 1871, had only nice things to say about the "Boobys" [boobies] he found there: "they must belong to a more Christian species than the rest who all laid their eggs on the ground." Quite the back-handed insult against sooties!

Chave referred to the atoll's Sooty Terns as "wide-awake[s]." He wasn't the only one. Apparently this was a common appellation Westerners gave to describe these noisy birds. "[T]hese kept up such a discordant screech all night," Chave wrote, "as to render sleep next to impossible." Dr. Streets of the U.S. Navy gave an even better representation of the annoying sooties, remaking on both their physical and audible presence: "...so great are their numbers that they form a cloud when driven from the ground, and their clamor deadens the roar of the surf." Now that's loud!

Marine biologist and writer Carl Safina, while conducting research for his book Eye of the Albatross (2002), used these poetic words to describe the various sounds heard one night at French Frigate Shoals: "the guttural grunts and honks of boobies, the brays and bill claps of the albatrosses, the murmurs of the noddies, and the Sooty Terns' squeaky I'm wide awake, wide awake." The Sooty's call sounds like the words "wide awake," but it's not hard to see why the name stuck with humans: a human on any one of these islands could not catch a wink of sleep because these damned birds kept them "wide awake" all night long!

Now. I got a bit side-tracked. You are a baby Sooty on Johnston Atoll. You hatch in April. There are 82,000 little ones just like you also hatching on these 10 acres (or so) of Sand Island (decades of landfill altered the island's geography in the mid-20th century). There are, perhaps, 300,000 total adults breeding on the island during the months February-July. But few eggs will hatch and few chicks will mature exactly according to their parents' highest hopes and dreams. By the end of April there are only 55,000 chicks running around, due to chick mortality. By June, after a 75-day fledging period (or so), you can fly! By July, just about all your peers are flying, too. You've got three weeks to practice flying before you'll abandon Johnston for many years. You'll truly fly almost non-stop for years until you are ready to return to this island, the place of your birth, and have your own little Sooty chicks!

A Sooty Tern chick at Tern Island, French Frigate Shoals
(Source: U.S. FWS @ Wikipedia)

The remarkable thing about Sooty Terns at most islands in the Pacific are their sheer numbers! At Johnston Atoll in the 1960s and 70s, perhaps 600,000 Sooties came to breed there annually. There might only be a handful of them poking around the islands in early winter, but by February hundreds of thousands of them came seemingly out of nowhere in for a landing, stopping here to lay their eggs. And come late summer those hundreds of thousands - and their new chicks - will be gone again. Other seabirds breeding at Johnston Atoll at that time came in numbers only as high as 6 or 7,000; nothing compared to the Sooties. And most birds bred in numbers more like 1,000 or less.

Why were/are there so many Sooties? That's a great question. (I'd like to know how many Sooty Terns there were in the 1850s when guano extraction began on these islands, but that data still needs to be put together.) I figure the Sooties' colonial habits have something to do with it. When they breed in numbers like those seen at Johnston Atoll, the piracy of Frigatebirds surely matter to the harassed individuals, but don't really matter at all in terms of the whole Sooty population. The piracy of rats are another story. It is clear that rats have extirpated breeding Sooty Terns from certain islands in the Pacific. It has even been suggested that as early as the 1850s - even before guano mining began - rats had caused the complete extirpation of Sooty Terns on Howland Island (but this is based on only sporadic human documentation of the island at that time).

The Sooty Terns are represented as one of the most annoying of seabirds, but I, from the view here in New York, find them stunningly beautiful. Often we consider the rarer birds to be more beautiful. We do this, I think, only because we tend to look harder at those things that are harder to see. Thus, Carl Safina is awed by Laysan Albatrosses, yet simply annoyed by the Sooties. Guano workers of the mid-nineteenth century would have found themselves similarly annoyed if not uncomfortably crowded by the breeding Sooty Terns. And they would have had horrible evenings trying to sleep while thousands of birds hovered above calling "wide awake, wide awake." As a historian, I find the Sooties most interesting because I am sure they were the most common seabird that the guano workers I am studying had interactions with. Historical ecologists might find it more interesting that a visiting ship captain saw a Red-Tailed Tropicbird - even just one - or that a shipwrecked sailor killed and ate an albatross. But for me, I love most when I read about the incessant racket of the circling "clouds" of birds overhead. I love imagining how the workers were kept up by the horrible noise all night, and how they were pooped on - again and again - all throughout the day. Loud, messy Sooties! Sooties, sooties everywhere!

A Sooty Tern colony in the Seychelles
(Source: Wikipedia)

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