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!
Excellent post - informative and fascinating!ReplyDelete
Wow! I learned a lot from this post; it was especially surprising to find out how resourceful the curlews are in terms of using various objects as tools. Thanks for yet another interesting, informative, and fun post! Mahalo!ReplyDelete