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!
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| 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.
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| 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!
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| 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!
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