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Wildlife Spy: Flight of the Western Sandpiper

TIP: Shorebirds have quick turnaround time in Alaska - look for them on northward migration in May and southward migration as early as the end of June

Posted: May 31, 2013 - 12:00am
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The food western sandpipers dine on changes with location. During migration, they feed in tidal mudflats, poking into shallow water or the mud exposed by an outgoing tide for tiny pink clams, marine worms and other tasty tidbits.   Courtesy image
Courtesy image
The food western sandpipers dine on changes with location. During migration, they feed in tidal mudflats, poking into shallow water or the mud exposed by an outgoing tide for tiny pink clams, marine worms and other tasty tidbits.

Spring brings bird festivals in Alaska, and this May, I slipped into the Kachemak Bay Shorebird Festival, in Homer, to check out the returning birds. I zeroed in on one of the main stars of the show for both this festival and the Copper River Shorebird Festival, in Cordova: the western sandpiper.

Although other species pass through, the western sandpiper has a lock on the largest numbers. Studies estimate nearly 4 million western sandpipers stop at the Copper River Delta in the span of about three weeks.

Kachemak Bay sees lower numbers of western sandpipers than the Copper River Delta, but the flocks of hundreds or thousands of birds are fascinating subjects to observe. This year, with the cold, late spring, the western sandpipers must have rushed to make their appearance. Flocks of several hundred arrived the Friday afternoon the festival started.

Your best chance of spotting western sandpipers in Juneau in flocks up to 1,000 or more is early May or mid- to late-July on the Mendenhall Wetlands State Game Refuge or at Eagle Beach. Western sandpipers have short, black legs and a black bill, medium-length for their size, with a slight droop in profile. In breeding season, they sport rusty red caps, cheeks and shoulders. Their white chests and flanks are flecked with black. When flocks are feeding, you often hear their trilling calls.

These sparrow-sized shorebirds only breed in Alaska and a small section of eastern Siberia. The stronghold of nesting western sandpipers is Western Alaska, with a few outposts along the North Slope. They winter along the coast from Washington state down to Peru on the Pacific Coast and from about North Carolina south to Surinam on the Atlantic Coast.

Unlike some of their larger shorebird cousins, western sandpipers are too small to pack on enough fat to fuel long, direct flights from breeding to wintering grounds in one stretch. Instead, they rest and feed at stopover sites along the way. The major sites include the Upper Bay of Panama, the coast of northwestern Mexico, San Francisco Bay, Grays Harbor in Washington, the Fraser River Delta in British Columbia, and the Stikine River, Copper River Delta and Kachemak Bay in Alaska. These sandpipers are very social little birds, gathering in flocks of up to thousands of their closest friends.

Spring migration is a whirlwind trip compared to the more leisurely weeks-long migration in the fall. Birds have a narrow window to raise their chicks in Alaska, and none of them want to waste any time. They only pause at a stopover for a day or two, just long enough to eat and fly. They rest often, napping in large groups between their tide-dependent feeding times. Often they balance on one leg, tucking the other into their feathers to regulate heat loss. Sometimes, a bird may hop a short distance on one leg. When I’ve seen this, it looks like it’s injured ... but don’t fall for the ruse. Usually, it just means the sandpiper wanted to nap in a different spot.

The food western sandpipers dine on changes with location. During migration, they feed in tidal mudflats, poking into shallow water or the mud exposed by an outgoing tide for tiny pink clams, marine worms and other tasty tidbits. In recent years, researchers discovered that many shorebirds, especially the smaller species such as western sandpipers, also engage in “snot-feeding.” On some mudflats, microscopic plants called diatoms and bacteria form a thin, energy-rich layer anchored in place by mucus, known as biofilm. Western sandpipers have bristles on the ends of their tongues that allow them to lap up the biofilm so fast, the action it is almost undetectable by the human eye. It’s thought that some chemicals in this gooey diet may help create the red color in the sandpipers’ feathers. Once the western sandpipers reach their nesting grounds on open tundra, they totally change their modus operandi: their prey changes to insects and larvae. This high-protein diet helps their chicks grow quickly.

Not all western sandpipers arrive in their summer home simultaneously. Males arrive first, so they can secure a good breeding territory. Usually they return to the same turf they had last year. Since there aren’t any trees to perch on, males fly into the air to belt out a buzzy, trilled song to stake their claim. If they haven’t found a mate yet, they have a different call to advertise their single status.

Females arrive a few days after the males, possibly to the same nesting territory from the previous year. When a female arrives on a male’s territory, he immediately starts trying to impress her. She usually ignores him and feeds or sometimes naps first. She may spend a few days playing hard to get. The male scrapes a potential nest into a rise in the tundra and the female tries it out, if he’s lucky. They may go through this ritual half a dozen times before the female decides which nest to use. As part of the courtship, the pair will preen each other’s necks. The male especially will preen the female while she’s test-driving one of his potential nests, so there is a little romance.

Like many shorebirds, western sandpiper chicks are mobile within hours of hatching. Being on the ground is a vulnerable position; as soon as the last chick hatches and dries off, the family is on the move. The chicks need about three weeks to grow and learn to fly.

Western sandpipers practice tough love with their offspring. The female may leave the family and head to feeding grounds with other females before the chicks can fly. Growing the eggs is energetically very costly for the female. To replenish her body enough to survive migration, she may delegate raising the kids to her mate. As soon as the chicks can fly, the male departs as well. The juvenile birds sometimes gather into flocks; they feed for another few weeks before they take off on their first migration south.

Adult male and female western sandpipers have different winter destinations, which may be different yet from where juveniles wind up. Female western sandpipers head south first, sometimes as early as late June. Males leave in early to mid-July. Juveniles depart by early August. Males winter the farthest north, presumably so they can return to breeding grounds as early as possible in the spring to grab a good territory. Studies have shown that about 70 to 80 percent of the western sandpipers wintering in California, Texas and northern Mexico are males, while the reverse is true in Central and South America. Juveniles tend to wind up at the extreme northern and southern parts of the wintering range.

It’s mesmerizing watching flocks of these small birds bend and stretch in various shapes over mudflats, seeing them only as a group. But when you look at the narrow, pointed wings of one bird flapping briskly by, it builds a much greater appreciation of the vast distances that small body covers every year.

• Beth Peluso is a freelance writer and illustrator and avid birder. She enjoys spying on wildlife across Alaska.

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