The shorebirds are coming - thousands of them - and one of the best places to see them is on the Mendenhall Wetlands in Juneau's own backyard.
Some 39 species in the plover and sandpiper families have been seen on the wetlands during the past 16 years. That includes Western sandpipers, which come in the greatest numbers by far, as well as pectoral and least sandpipers, golden plovers, dunlins, dowitchers, turnstones and surfbirds. Greater and lesser yellowlegs are easy to see, especially along the Airport Dike Trail. And you might even encounter a rare shorebird such as one of the godwits, or an Asiatic stray such as a sharp-tailed sandpiper, a ruff, or a long-toed stint.
Where these birds come from and how they get here is nothing short of remarkable. Most of the shorebirds we see each spring have traveled thousands of miles after wintering in places as far away as South America, New Zealand and islands of the Pacific Ocean. On their long journey to breed and nest in northern and western Canada and Alaska, they typically migrate day and night. Some travel at altitudes of 15,000 to 20,000 feet, where thin air helps increase their speed. And they sometimes travel at astonishing speeds.
Northbound dunlin, passing a light plane, have been timed at 100 miles per hour. When researchers radio-tagged a number of western sandpipers they discovered one female flew at least 50 miles an hour on a roughly 2,000-mile migration.
Flying thousands of miles, often nonstop, consumes a tremendous amount of energy and body fat, so resting and refueling stops at places such as the Mendenhall Wetlands are critically important if birds are to reach their northern breeding grounds.
What is it that makes the Mendenhall Wetlands so attractive to shorebirds? According to Scott Weidensaul, who writes about shorebirds in "Living on the Wind," "Most of the world's surface is useless to a shorebird - too wet, too dry, too forested, too mountainous, too farmed, too urban, too this or that. Much of the wetland habitat on which many species depend has been lost. So the relatively few places that still suit the birds' needs are important beyond measure."
The Mendenhall Wetlands is just such a place. It is one of only three places in Southeast Alaska that the Alaska Shorebird Conservation Plan recognizes as crucial to shorebirds as a stopover during migration. The other two are the Stikine River Delta and the Yakutat Forelands.
A number of people in Juneau are studying how birds of many different types use the wetlands. In one project sponsored by the U.S. Fish and Wildlife Service and conducted through Discovery Southeast, Discovery naturalist Richard Carstensen and researchers, including Mary Willson, are studying areas of high bird activity on the wetlands, including use of the area by shorebirds and waterfowl.
In collaboration with that project, Aaron Baldwin, a graduate student at the University of Alaska, is also studying the abundance and distribution of invertebrate prey. Baldwin's work is especially important to understanding shorebird distribution because invertebrates such as amphipods, worms and small clams are the major foods on which migrating shorebirds depend.
Baldwin has found that invertebrates are very numerous in areas of high bird use on the wetlands. In beds of mussels and fucus, a common marine plant, and in areas of mixed sand and mud, he has found polychaete worms, isopods, periwinkles, small clams and amphipods, which are small shrimp-like invertebrates.
On one of Baldwin's field trips, the abundance of amphipods was surprising. He turned over a clump of fucus, and there were so many amphipods it looked like a shrimp cocktail. Some were nearly as large as Petersburg shrimp.
Dogs and shorebirds
Some of the areas offering the most food for shorebirds in the Mendenhall Wetlands are right alongside the Airport Dike Trail.
An unleashed dog romping beside the trail will disrupt vital feeding for shorebirds as well as decrease the chance for people to see the birds.
Loose dogs also chase shorebirds away from intertidal areas near the dike and on the mudflats.
Please keep your dogs on a leash at least from mid-April through May. Those valiant migrants that pass through our backyard for just a few weeks each spring need all the help they can get.
In one area of mud flat near the gazebo on the Airport Dike Trail, Baldwin found a density of corophium - a tiny amphipod - that translates to roughly 20,000 amphipods per square meter. That's important because one study in the Bay of Fundy found that some sandpipers feed almost exclusively on corophium. Each sandpiper consumed an estimated 30,000 of these amphipods per day.
Some of the rare places that provide that level of abundance are being mapped by the Western Hemisphere Shorebird Reserve Network, a collaboration of more than 140 public and private organizations in seven countries. The network compiles data, calls attention to places critical to shorebirds, and provides educational materials for teachers, students and the general public.
You can read more about the network and regional shorebird conservation plans, including the Alaska one, at www.manomet.org.
Bob Armstrong and Marge Hermans are avid birders and Armstrong is one of the researchers studying bird activity on the Mendenhall Wetlands. Southeast Wild is written by members of the Juneau Audubon Society. Monthly meetings are held the second Thursday of each month from September through May. Contact Audubon at firstname.lastname@example.org.
© 2016. All Rights Reserved. | Contact Us