Saturday, September 16, 2017

Real Snowbirds

My parents retired to Florida some years back and I remember, during one of my first visits, them telling me about the “snowbirds”, the term used to refer to folks that spent their winters down in the Sunshine State and returning to the north each summer to avoid the southern heat. In our modern world, where one can simply hop on a commercial jet and make the 1,100 mile journey from New York to Miami in just a couple of hours, maybe even sipping a cocktail and munching peanuts while you sit in a cushioned seat and watch a movie, , this is no great feat. The word snowbird though, has been around for a much longer than Miami Beach – since 1674, according to Merriam-Webster – and once was used to refer to bird species seen only during the winter months.

Unlike many subtropical parts of the U.S., fall does not bring with it gray-haired flocks with golf clubs and tennis racquets, but we definitely do have our snowbirds. And truly fine neighbors they are, so let me introduce them to you!

Ruddy Turnstone on Sand Island, Midway Atoll (Photo by Jon Plissner)
Although a variety of bird species occasionally find their way to Midway during fall migration (which actually begins in late July) four are very regular and fairly abundant. The ‘Akekeke or Ruddy Turnstone is a small, stocky, calico-colored shorebird with bright orange legs that breeds throughout the Arctic – including large swaths of Alaska, Canada, Greenland, and Russia. After breeding, adults head south and are followed shortly thereafter by the young of the year where they spend summers on coasts of every continent on earth, except Antarctica. This is a truly wide ranging bird species so it’s no wonder we find them here on Midway. Although typical habitat for turnstones is rocky shorelines, at Midway they are “habitat generalists”, and you can find them pretty much anywhere on Sand Island. When I walk to lunch I often find myself being escorted by a few turnstones on the path. Despite their short, stubby, legs, they are surprisingly fleet of foot. If I walk too fast though, they take flight, revealing a striking pattern of black, brown, and white on their backs. Though turnstones feed mostly on insects on their breeding grounds, during the winter they’ll eat pretty much anything: mollusks, crustaceans, worms, insects, and even dead fish. The Ruddy Turnstone’s ability to take so many different kinds of food may be credited to its diverse modes of feeding which include: routing through seaweed, turning stones with its feet (hence the name!), digging holes into and probing the ground, hammering with its bill, and pecking. The Ruddy Turnstone probably finds its time on Midway pretty relaxing. With mild weather, no chicks to feed, and no predators to be worried about, they seem to be living a pretty charmed life. But when spring comes, some biological urge compels them to take to the skies again and return to their breeding grounds in the Arctic. 

Adult male Pacific Golden Plover on Sand Island, Midway Atoll. Note that this photo was taken while the bird is in the midst of molting from its breeding plumage to winter plumage (Photo by Jon Plissner).

Another regular winter visitor is the Kōlea or Pacific Golden Plover, an elegant shorebird with long legs and a short bill that, like the turnstone, seems to be found nearly everywhere on Sand Island –runways, lawns, beaches. etc.  – where it walks about, stopping occasionally to eat some insect or other tasty morsel. This species of plover is somewhat unusual as shorebirds go in that males and females look quite different, at least for part of the year. During the summer breeding season, male golden plovers wear nearly black feathers from their face down through their belly, ringed by white, and the feathers on their backs become tinged with gold; at this time they are easily distinguished from the more drab females. After arriving on their winter grounds, both males and females molt and grow buff colored feathers on their face and breasts while their backs and the tops of their heads are mottled with brown and gold. At this point they are pretty much indistinguishable. When darkness falls on Midway, plovers may issue a fantastic warbling, musical, call before returning to communal roosts where they spend the night.

Pacific Golden Plovers nest high above the Arctic Circle, from Alaska to Siberia, escaping the boreal winter each fall by heading south where they can be found almost anywhere along the western coasts of the America from British Columbia to Chile. They also make their way to nearly all Pacific Islands as well as the coasts of China, Japan, Thailand, India, Sri Lanka, and Iran. Did I mention northeast Africa? During the winter Pacific Golden Plovers inhabit nearly half of the globe, and accomplish this by undertaking an epic and mind-boggling annual migration – sometimes flying thousands of miles non-stop over open water. Our Golden Plover has two close relatives, the American Golden Plover and the European Golden Plover, and they sometimes encounter each other at the edges of their breeding ranges. Sometimes a Pacific Golden Plover will mix in with a flock of its cousins and travel south with them, taking them far outside their usual winter range, for example, Europe. This is a bird that really gets around!

Two Wandering Tattlers hunt for food in an artificial wetland on Sand Island, Midway Atoll (Photo by Jon Plissner)

The ‘Ūlili or Wandering Tattler is a stocky, long-legged, grey shorebird that nests in remote montane valleys, carved by glaciers,  in Alaska, Canada, and the Russian Far East. Compared to other shorebirds, there is scant knowledge of this species, a consequence of its small numbers (estimated at 10,000 to 25,000 worldwide), cryptic coloration and small numbers. Even if you made the trek to Denali National Park in Alaska, a place where they are known to breed, you might not ever see one, due to their solitary habits and secretive behavior. The Wandering Tattler heads south in August and, like the other snowbirds, fly to their winter homes in the Pacific Islands – including Hawaii, Galapagos, Micronesia, and New Guinea – and along the coasts California and  Mexico. Here on Midway we are very lucky to be able to reliably observe this fascinating bird. Unlike the Ruddy Turnstone and the Pacific Golden Plover, tattlers stick pretty close to water.  I often see them on the beach next to the Cargo Pier and at “Catchment” (an artificial wetland near the runway). They will even hang out on emergent portions of the coral reef that rings the atoll. Wandering Tattlers are thought to be territorial in the winter – birds are typically seen alone and widely and regularly spaced on beaches. They always seem to be concentrating on finding food, occasionally probing their long, stout bills in the sand or mud, looking for invertebrates, including crabs, snails, and shrimp. Because they stick to the water, tattlers probably have a more specific diet than some of the other Midway snowbirds. Both their English and Hawaiian name derives from the sound of their call.

A Bristle-Thighed Curlew struts its stuff on Sand Island, Midway Atoll (Photo by Jon Plissner)

I have saved my favorite snowbird for last. The Kioea or Bristle-thighed Curlew is a large shorebird  that nests in the Alaskan tundra. It seems to be pretty picky about where it breeds though favoring just two areas between the Yukon River and the north Seward Peninsula. After raising their chicks, curlews depart their breeding grounds and head for the Yukon Delta where they spend some time fattening up for the long trip south where they escape the Alaska winter on various oceanic islands; from the Northwestern Hawaiian Islands in the North Pacific to the Pitcairn Archipelago on the other side of the equator. The distance travelled by these birds during their annual migrations is nothing short of incredible: over 2,700 miles for birds travelling to Midway and over twice that if they decide to continue to the southernmost portion of their winter range. This distance is not far short of the distance travelled by the Bar-tailed Godwit which holds the record for nonstop avian flight (7,145 miles). Seeing a Bristle-thighed Curlew for the first time you might not realize how capable a flier it is, but apparently they can outfly falcons!

After the long and arduous journey to its winter grounds, the Bristle-thighed Curlew begins the long task of replenishing its energy stores. It very opportunistic with regards to its diet: crabs, spiders, roaches, moths, carrion, fish, and seabird eggs have all made their way into the stomachs of hungry curlews at Midway. The Bristle-thighed curlew is unique among shorebirds in its ability to use tools while foraging, picking up pieces of coral and using them to smash holes in eggs.

Bristle-thighed Curlews begin arriving at Midway in mid- to late-August and can be seen nearly everywhere on Sand Island, from the backyard to the beach.  When they first arrive in the spring they seem to hang out in groups but eventually go solo, perhaps even defending small winter territories. You may see a bird standing on top of a dune or other high point calling. Who are they calling and for what reason?  I’m not sure but sometimes I call back with my own whistle and the curlew will usually reply. These birds are subtly beautiful and very fun to watch as they walk, stealthily, gracefully, in pursuit of their prey, stopping occasionally to poke their long, curved bills into the sand or a clump of grass. There is some speculation here that the groups of birds observed at the end of summer might be just passing through.

Like many migratory birds, Bristle-thighed Curlews molt their feathers on their winter grounds so as to have a fresh set for their return flight up north. Bristle-thighed curlews are unusual though in that they sometimes lose so many feathers at once that they become temporarily flightless. This would put a bird at a serious disadvantage if it were spending the winter, say, in Florida. But if your winter home is Midway or another island without foxes or cougars to bother you, I guess it can be a good way to go.

After months on their winter grounds, a Bristle-thighed Curlew, if it has done well, has put on enough fat to return to its summer home up north. These birds can live for over 20 years, which is pretty long for a shorebird, and thus might travel over 100,000 miles in its lifetime.

How birds developed the ability to travel such long distances between their wintering and breeding grounds has puzzled scientists for decades. One theory, dubbed the Northern Home hypothesis, is that long-distance migrants evolved from more sedentary ancestors that lived in temperate areas and they gradually ventured farther and farther south during the winter to escape the harsh conditions. Others have argued that it’s just the opposite, and long-distance migrants evolved from tropical ancestors that learned to take advantage of the seasonal abundance of foods – insects, for example – found during the summer months in northern lands (i.e., the Southern Home hypothesis). A recent study by Benjamin Winger and colleagues  (seriously, the guys’ name is “Winger!) found more support for the for the Northern Home theory, at least for songbirds, but seems to leave us with a lot of unanswered questions when it comes to evolution of migration in shorebirds.

Many millions of birds engage in long-distance migrations each year. Each bird that suddenly shows up somewhere is a small clue that reveals a little bit about this amazing, global, biological phenomenon. I sometimes think birders are weird for getting so excited about seeing – what often seems like – yet another drab shorebird that plops down on midway for a few days. But while researching the natural history of these snowbirds, I have come to better appreciate how meaningful these sightings are. And though micro-GPS units, satellites, and radar are all now used to help decipher patterns of bird migration, individual sightings made by keen-eyed birders still make a large contribution to this aspect of science.

While the human variety of snowbird may not be the most interesting or impressive thing that evolution has produced, these real snowbirds that visit Midway each year are not only beautiful and interesting to watch, but they are also true testaments to the incredible adaptations that have evolved since they first appeared on our planet some 60 million years ago. And even though you might not have the good fortune to wake up to a Bristle-Thighed Curlew calling Chiu-eet  in your backyard, no matter where you live you probably have your own snowbirds to enjoy. Learning more about where they live during the rest of the year and why they travel such long distances can make backyard bird watching even more rewarding. For me, it has also piqued my curiosity regarding the places where these birds spend their summers and I am anxious to take a trip north to check it out sometime.

Postscript: Although I typically like to use my own photographs in this blog, getting good photos of the snowbirds proved a little bit too challenging for me and my camera (which is actually a phone).  There is a biological explanation for this: while the seabird species that breed on Midway seem to be unafraid of people, the winter visitors, all of which breed on mainland North America where they evolved with humans and other mammalian predators, are much more wary and thus more difficult to photograph. So rather than include a bunch of blurry photos that would not do these birds justice, I decided instead to use some terrific photographs taken by my Midway colleague and friend Jon Plissner. Mahalo Jon for kindly allowing the use of these photos and also for the great conversations we’ve had about the avian life of the atoll! 

Sunday, August 20, 2017

A-hole of the Skies

If, in reading my previous blog posts, you’ve gotten the impression that birds are inherently noble or good, let me disabuse you of that notion by telling you about the Great Frigatebird (Fregata minor).

An adult female Great Frigatebird soars above Sand Island on Midway Atoll.

We generally admire predators, understanding that that they need to kill other animals in order to survive. After all, everyone’s got to eat and most of us humans sacrifice the lives of other creatures for our daily sustenance. And it’s certainly true that most animal species, including our own, sometimes find themselves in conflict with others of their kind, so when fights break out between individuals over territory or mates, we tend to shrug our shoulders and attribute such violence to Darwin’s theory. Albatross, for example, are generally peaceful creatures but at the start of the mating season, things can get pretty ugly.

What is it about the frigatebird then that illicits such negative reactions from people? Why do I often find the word “asshole” forming on my lips as I watch them fly by?

In terms of public image, frigatebirds face some real challenges. First, they are very large and kind of scary looking. Cloaked in black feathers and having a wingspan exceeding 2 m (80 inches) and a long hooked beak, they are imposing looking as they circle above Midway in vulture-like fashion. Unlike vultures, they are not scavengers, which becomes apparent when they suddenly burst into rapid flight chasing down a seabird as it returns from a foraging trip to sea and harasses it mercilessly until it drops whatever food it's carrying. Then, before the regurgitated fish or squid hits the water, the frigatebird swoops down and catches the morsel in mid-air. A pretty clever trick, really, and it sure beats having fly out into the open ocean to catch your own food. In biological jingo this is known as kleptoparasitism, a portmanteau of klepto (Greek for stealing) and parasitism (to harm without killing). The Hawaiian word for this species, in fact, is ‘Iwa, meaning thief.

Watching frigatebirds engage in their thieving ways must surely rank as one of the most amazing wildlife spectacles, and on Midway this behavior is very easy to observe, especially this time of year, when frigatebirds are nesting and must feed not only themselves but also their hungry chicks. My favorite place to watch frigatebirds is at the Cargo Pier where you can sit as the sun sets, drink a beer or three, and get a really good view of the action. Just look for a Red-Footed Booby or Red-Tailed Tropicbird heading towards land and there’s a decent chance you’ll get to see a chase. (Male frigatebirds pursue sooty terns and noddies as well, but for whatever reason this seems more difficult to observe.) For the victim there’s a lot at stake – losing the food they are carrying might diminish the bird's chance of successfully fledging a chick – so they don’t give in easily. The result is often a truly spectacular aerial chase in which the booby or tropicbird attempts every flying maneuver it has in its repertoire. The bird in pursuit flies as fast as it possibly can, then suddenly twists and turns to evade its pursuer. Unfortunately for boobies and tropicbirds, the frigatebird possesses exceptional flying skills, a consequence of its large wing area to body mass ratio as well as a very long forked tail which makes it incredibly agile for its size. Frigatebirds also often attack in small “gangs”, making it even less likely the bird being pursued will succedd in escaping.

Frigatebirds soar high among White Terns scanning the skies for their next “victim” from which to steal a meal

Reasons to despise the great frigatebird don’t end there. These birds have an unsavory habit of eating eggs or small chicks (especially terns and noddies) when a nest is left unguarded.  I’ve seen them flying with Sooty Tern chicks in their bills on Eastern Island. They apparently will engage in cannibalism too, stealing eggs or chicks from other frigate nests. Frigatebirds may also attack vulnerable fledglings when they are trying to learn to fly. I once watched two frigates torment a young Bonin Petrel that was floating in the water off West Beach; they dove at the petrel repeatedly for several minutes, sometimes grabbing the fledgling, flying up a few feet, and then tossing it violently. Eventually the frigates tired of the game and left the petrel there in the water, looking much the worse for wear (I’m guessing it died).

Frigatebirds thieving ways are not limited to stealing food. Both male and female Great Frigatebirds work together to construct their nests; the male gathering the nest material and bringing it to the female who does the bulk of the building. Sometimes though, a male will find it easier to steal nest material from other birds rather than collecting it himself. Red-footed boobies, which often nest in very close proximity to frigatebirds, are a common victim. The situation is even worse if you’re a Black Noddy though, as the frigatebird is known to steal their entire nest! Then there is the issue of the nest itself which, because the frigatebird chicks lack the ability to eject their feces away, becomes covered in shit and quite stinky as time goes on.

Great Frigatebirds prefer to nest in shrubs or trees. On Eastern Island at Midway Atoll they find suitable habitat atop tree heliotrope (Tournefortia argentea).

So is the frigatebird really an avian A-hole? When I the idea of writing a blog post about the Great Frigatebird was hatched in my mind (sorry!), I was pretty convinced that this was so. But as I was researching this species I discovered that the story was much more complicated.

Frigatebirds, it turns out, share some of the same admirable traits possessed by albatrosses. Parents are monogamous (at least during a given breeding season), engage in interesting, if not completely endearing, courtship behavior, which include various postures including the male’s display of its gular sac. Both male and female equitably share in the incubation, brooding, and feeding of their one and only chick. This is no small feat as it can take over six months to raise one. Great Frigatebirds might even hold the record for avian parental dedication. Unlike albatrosses and many other seabirds, whose care of their chick ends at the time of fledging, adult frigatebirds continue to feed their slow-growing offspring for up to a year after they leave the nest.

A male Great Frigatebird displays its gular sac in an attempt to attract a female

OK, maybe you’re saying "so sure they are good parents but what about the stealing bullshit?". Having grown up in a neighborhood with a lot of mobsters I know what you're saying. Some of them were good parents too when they weren't out stealing and killing!  Well it turns out that kleptoparasitism accounts for just a small part, by some accounts just 5%, of the Great Frigatebirds diet, meaning that they obtain the bulk of their food – squid and flying fish, primarily – by (anthropocentrically-speaking) honest means. 

Frigatebirds certainly should be admired for their incredible flying abilities. Here on Midway you can often see them hovering very high in the sky, like large black kites, riding the air currents and rarely flapping their wings. Like albatrosses, they engage in a flight technique known as dynamic soaring, a sophisticated means of using differences in air speed to fly quickly and efficiently; frigatebirds cruise nearly effortlessly at speeds of up to 50 km / hr (30 mph). The frigatebird’s aerial prowess has enabled them to colonize a large swatch of the tropical and subtropical Pacific Ocean, from the South China Sea, to the Great Barrier Reef, and to Mexico and Christmas Island in the South Pacific. Some populations are even migratory. Midway lies just about at the northern extent of their range. This hyper-adaptation to a flying lifestyle does not come without a cost. The Great Frigatebird’s small legs and feet create difficulties for them when trying to take off; they don’t land in the water because if they did they might get stuck there.

Living around frigatebirds is definitely a unique opportunity and I feel a little embarrassed at not having taken the effort to look beyond the stereotypes and appreciate their other behaviors until now, over a year since beginning my assignment here. It makes me wonder how much stereotypes and lack of information, limit my appreciation of other species (or even my fellow humans!). An important reminder, I think, to question your assumptions and spend more time questioning and learning and less time judging.

Additional reading for the exceptionally curious:

Gilardi, J. D. 1994. Great Frigatebird kleptoparasitism: sex-specific host choice and age-related proficiency. Condor 96:987-993.

Monday, July 31, 2017

Wandering Glider

If I told you there was a species that flies thousands of miles each year, stopping at Midway each spring to breed at Midway Atoll, you’d probably think I was talking about something covered in feathers. And you’d be wrong.

Among the insects are some species known for their long migrations. The famous Monarch butterfly (Danaus plexippus), for instance, travels back and forth each year from breeding areas in northern Great Plains to their overwintering sites in southern Mexico. The Monarch seems to have never made its way to Midway and, in fact, just a single species of butterfly can be found on the atoll, the Painted Lady (Vanessa cardui). The amazing insect voyager that I want to tell you about, though, isn’t even a butterfly.

The Wandering Glider, known also as the Globe Skimmer (Pantala flavescens), is a large dragonfly species that occurs across a wide swath of tropical and temperate areas of the Americas, Asia, Australasia, and Africa as well as oceanic islands. The wide distribution of this species was not fully appreciated until recently when it was discovered that they make incredible, long-distance migrations. The “population” studied, migrated each year from India to Africa, stopping in the Maldive Islands along the way, following the monsoon rains and then returning via the approximately same route. It is part of an elaborate, multi-generational, movement that may exceed 18,000 km (11,185 mile) in total distance and which requires individual insects to journey over 6,000 km (3,728 mi), including a 3,500 km (2,175 mi) non-stop leg over the open ocean. 

How do they do this? By following the winds. This is not a simple thing to do though as often winds are blowing in the opposite direction that they need to travel. So they exploit weather fronts, often flying at altitudes exceeding 1,000 m (3,281 ft). Their large, long wings make them very strong fliers; they've even been seen in the high mountains of the Himalaya at elevations exceeding 6,000 m (19,685 ft). The globe skimmer, it turns out, has the longest known migration of any insect! 

A Globe Skimmer in Oahu, Hawaii (Photo credit: Forest and Kim Starr)

I remember how surprised I was when I first saw dragonflies on Midway last summer hovering and chasing each other just outside my house. It led me to do some research on them which turned out to be extremely enriching.

Decades of inadvertent introductions of exotic insect species – arriving in food, plants, soil, or other items brought to the atoll – have had significant effects on the arthropod fauna of Midway. Over a dozen surveys of insects and other arthropods have been conducted at Midway, beginning with a study done by Henry Palmer and  George C. Munroe in 1890, creating a long-term record of the extensive introductions (and even some extinctions) that have occurred.

No dragonflies were encountered until Gordon Nishida noticed the Globe Skimmers while conducting an extensive arthropod study in the late 1990s. Because of this I had thought, at first, that the skimmers probably weren’t a native species but Nishida listed them in his report as being “indigenous”, which is basically to say that they occurring here at Midway naturally.

All dragonflies need fresh water in order to reproduce. Globe Skimmers traveling between India and Africa sometimes stopover in the Maldives and other islands that lack freshwater, perhaps to rest before moving on. Are the Midway skimmers breeding here or are we just a stopover site? Two pieces of evidence suggest the former. That the Globe Skimmer was not known at Midway until 1998, combined with the fact that this date corresponds well to the introduction of Laysan Ducks to Midway, an effort that required the construction of artificial freshwater seeps and ponds, argues pretty well that they are breeding on Midway. This shouldn’t be too hard to verify – just some aquatic invertebrate surveys. I will admit to not having put enough study into the situation. An hour long sit-down down by one of the ponds might be enough to yield an answer as Globe Skimmers, like many other dragonflies remain connected to each other during their mating flights.

And if these dragonflies are breeding on Midway in manmade ponds, does that really mean they are native as was suggested by Nishida? I guess it depends on your criteria, but in either case it is a good illustration of some of the existential challenges faced by biologists working in these kinds of island ecosystems.

The Globe Skimmer has been featured on postage stamps from several nations, including Botswana and the remote Pitcairn Islands, a British Territory in the South Pacific.

A recent genetics study by Daniel Troast and others showed that the peregrinations of Globe Skimmers are so extensive that it may represent a single worldwide population among which genes flow freely. A truly global insect!

Two additional dragonfly species have been recently observed at Midway by Forest and Kim Starr, the Green Darner (Anax junius) and Black Saddlebags (Tramea lacerata). Both of these species are also known to migrate long distances but probably never stopped for very long at Midway prior to recent times when surface freshwater ponds and seeps were constructed. Similar to plants, the insects of Midway tell a story of continual change and illustrate how effectively species can discover and adapt to changing conditions, abilities that will be as important as ever in a time of rapid environmental change.

Postscript: If you are interested in learning more about the Globe Skimmers I recommend you check out the TED Talk by Charles Anderson. Also, this is the first time I've posted a story without a single photo that I've taken. Turns out my photographic skills and patient were not sufficient to capture a decent image of one.

Monday, June 19, 2017

One Good Tern Deserves a Noddy

An adult white tern on Midway Atoll 

Not long after arriving at Midway I had an un-nerving experience.  I was walking down the road when I suddenly realized that I was being followed. Not by a person but by several small, brilliantly white, birds with long blue bills. Their wings beat quickly as they flew just a foot or two over me making hoarse “wreck wreck wreck” sounds. They seemed to want to land on my head or my shoulder and so I extended my hand to see if one would light, but they didn’t seem interested in getting quite that intimate. This is typical behavior for manu-o-Kū – the white tern!

White (sometimes called “fairy”) terns are small seabirds found across a wide portion of the tropics including the Atlantic, Pacific, and Indian oceans.  They occur throughout the Northwestern Hawaiian Islands but if you are visiting the main Hawaiian Islands you will find them only on the south shore of Oahu where a small population persists around Honolulu. At one time, white terns probably also occurred on the other main islands (e.g., Kauai) before cats, rats, dogs and other predators wiped them out. Unlike many seabirds that nest on the ground, white terns like to nest up high in shrubs or trees. And they don’t actually build a nest, they simply find a place that they think will hold an egg securely (the female lays just one) and “nest” there. On Midway typical nesting sites for white terns include ironwood trees and shrubs like plumeria and tournefortia, especially where a branch forks creating a small depression. But they also nest on air conditioners, windowsills, garbage can lids, utility boxes, and other odd places. After a short fall hiatus, “tern season” begins in December with the first chicks born around March and peaking during the warm summer months of June, July and August.

The white tern holds a special place for the Hawaiian people which is reflected in its native name (manu means bird and is one of the four great Hawaiian gods). Moreover, the Hawaiian people have likely had a close relationship with this bird for hundreds if not thousands of years. Ancient Polynesian voyagers used white terns to navigate as they are one of the most reliable indicators of land. Compared to albatrosses and other far-ranging seabirds, white terns stick pretty close to home (within a hundred or so miles). Like a suburban commuter, terns leave their islands each morning to spend the day at sea foraging, returning each evening. If the navigator of a canoe wanted to find land, he’d look for white terns flying and, depending on the time of day, either head in the direction they seemed to be coming from (morning) or follow it back towards land (evening). Terns follow us and vice-versa. 

My experience with white terns at sea is mostly limited to swimming where I often find myself being followed by a small, raucous flock. What is it that makes the tern want to follow people whether on land or in the water?  I’m not sure anyone really knows. It could be that they are just very curious creatures. This would jibe with one of their other interesting behaviors which is to sit on a windowsill looking inside towards the occupants. Many a morning I have eaten breakfast under the dark black, watchful eyes of one or two white terns.

A pair of white terns investigating me from the windowsill of my house

I have also enjoyed watching white terns forage from my favorite relaxation spot out on the cargo pier. Terns fly low over the water looking for small fish near the surface and then swoop down quickly to capture them in their bills. When foraging to feed their chicks they have to gather several fish at a time and somehow they are able to do this – catching fish when they are already holding one or more crosswise in their bills.

Everything about this bird seems surreal. Its pure white plumage punctuated with blue beak, legs, and feet. It’s habit of fluttering around you like some spirit animal. Like most other native birds on Midway, white terns have virtually no natural predators and as a result do not seem to have much fear of people and, thus, can be approached at very close distance allowing you to really feel a part of their world. This extends to their sex life as well and it is common to see birds engaged in either foreplay or copulation, the former of which consists of intense, alternating, preening of one another. White terns are thought to pair for life, which can mean a very long time and courtship behaviors – which includes high altitude “couples flights” help maintain their pair bonds. And then there are the chicks. One day there’s an egg on your windowsill and the next you find a tiny white and brown ball of fluff with oversized, webbed, feet.  The parents share equally in both incubation and feeding. Parents fly out to sea and return with a beakful of a whole fish which seem impossibly large for the chick to swallow but the little fluff ball somehow always manages having what seems like insatiable hunger. As the chick grows, the size of the fish brought to it increases commensurately.

It takes about 48 days after hatching before a chick is ready to fly.  Clockwise from upper
 left: White tern egg on windowsill; a newly hatched chick; 2 week old chick; 1 month old chick.

During the summer it’s sometimes necessary to relocate a chicks and raise them in captivity. This happens when some project – for example, tree removal – eliminates the chick’s “nest site”.  As the chick's parent can no longer find it, the chick must be fed by hand. Each day volunteers make three trips to the “white tern nursery”, located just down the road from the office, where branches have been affixed to large ironwood trees to create safe places for the chicks. Volunteers then feed the chicks regular meals of Great Lakes smelt, by hand, three times a day until the chicks are big enough to feed on their own. This is, without doubt, one of the best jobs there is on Midway as when the chicks get big enough to fly they actually follow the lucky fish dispenser back and forth from the office begging for treats.

Fledgling white tern chicks swoop down to take smelt from the hand of
Fish and Wildlife Service volunteer Aisha Rickli-Rahman

It seems that nearly everything about the white-tern lends itself to superlatives; and even the scientific name of the species – Gygis alba – reveals the sublime effect this bird seems to have on the imaginations of those lucky enough to spend time around them:  the genus, Gygis, is a variation of the ancient Greek word “guges” which means “mythical bird”.

So maybe at this point you’re wondering where the “noddy” ties into this story or, maybe, you’re even cynically thinking that in the title of this post I have crassly sacrificed good natural history for the love of bad puns. Fear not! Another name for the white tern is “white noddy”, noddies being a collection of taxonomically-disparate, fork-tailed seabirds in the family Laridae.  White terns are not the only noddies on Midway as we are “blessed” with both brown noddies and black noddies not to mention several species of terns – sooty tern, gray-backed tern, little tern, and least tern. Clearly, I don’t have time to do justice to all of these species here but maybe I can at least provide a proper introduction.

Black and brown noddies, as the name would suggest are most similar to white terns in terms of habitat and behavior. Both are common at Midway and, if they were easier to tell apart, I might be able to tell you more about how they differ. My understanding is that the black is less common as it is an obligate-tree nester while the brown noddy can nest in either tree or on the ground. Brown and black noddies are more likely to form small flocks than is the white tern and gangs of them can often be seen on the beach this time of year. These birds seem to share the predilection of white terns for following swimmers and they also often accompany me on swims.

A brown noddy perches on an old ironwood stump on Eastern Island (Midway Atoll)

Let me also tell you about the sooty tern!  These easily-riled birds are not common on Sand Island but are found in astonishing abundance on the other two islands of the atoll where people are scarce. Sooty terns are gregarious ground nesters that form large colonies on Eastern and Spit Islands. During their nesting season – which lasts from April until October – they blanket areas of the atoll and must be avoided at all cost. Should you fail to be pay proper attention and happen to walk too close to one of their colonies you will trigger them to take off, creating a swarm of thousands of screaming birds. You may be temporarily deafened and notice that one of them is now swooping down and try to take a piece of flesh from your face! You may then also suddenly find yourself walking among their well-camoflaged eggs and  praying that you don’t accidentally step on one. Gray-backed (or spectacled) terns are rarer than the Sooty tern, but no less easily agitated and tend to nest around the edges of the sooty tern colonies. They must also be treated with extreme caution.

As for the final two terns on our list, the little and the least (seriously, who comes up with these names), they are both pretty rare and exciting to see.  Being the mediocre birder that I am, I have little to report but a few random sightings that I probably would not have even noticed were it not for the astute observations of others. But they are here and the breaking news is that the least terns are currently nesting!

If you are a regular reader of this blog you may have thought, until now, that Midway was all albatrosses and petrels.  I hope that this short detour into the lives of other important and interesting seabirds that inhabit the atoll gives you a more complete appreciation of the bird life here. And there is more!  You can look forward to a couple more bird-related blog posts in the future.