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Chickaloon Flats through a shorebird's eyes

Posted: March 28, 2013 - 3:34pm
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Greater and Lesser Yellowlegs forage in a shallow slough during an outgoing tide.
Greater and Lesser Yellowlegs forage in a shallow slough during an outgoing tide.

A Lesser Yellowlegs leaves a brackish marsh off the Guiana coast of northeastern South America and begins its spring migration by crossing the Gulf of Mexico. Over the next couple weeks, it stops to rest and refuel at various stopover sites enroute to south-central Alaska in late April. Approaching Chickaloon Flats, the yellowlegs detects the familiar vast mudflats, bands of vegetation, and network of sloughs. But it’s the presence of scattered shallow ephemeral pools that makes this a suitable stopover. Stop here or go elsewhere.

Despite close proximity to Anchorage as the crow flies, this 24,000 acre tidal mudflat on the northern edge of the Kenai National Wildlife Refuge goes almost unnoticed by most people. Chickaloon is a protected estuary that serves as an important stopover area for birds migrating along the Pacific Flyway. For my master’s research on shorebird migration, I was fortunate to spend two field seasons living with the wildlife and mud of this remote gem.

Shorebirds travel thousands of miles round-trip from nonbreeding to breeding grounds in pursuit of seasonally-abundant food and nest sites. As spring migration begins, birds purposefully make their way through a continental network of migratory stopovers to their breeding grounds. Chickaloon is one of those unique stopovers.

Roland Quimby, a graduate student at the University of Alaska Fairbanks, was first to document bird use of the different vegetated communities on this mudflat in the early 1970s. After a nearly 40-year gap in ground surveys, my research confirms the clear significance of Chickaloon Flats as a migratory stopover.

I observed 95 species of birds from spring through fall of 2009 and 2010. Of 73 shorebird species recorded in Alaska, Chickaloon hosts 23 of them! And as many as 5,638 shorebirds stopped daily during peak spring migration (end April–end May), and upwards of 20,297 each day during fall migration (early July-Aug).

To delve further into shorebird migration and the migratory link that Chickaloon provides, I used stable isotopes to provide insight on potential breeding and nonbreeding origins of six species. The basic idea of stable isotopes is “you are what you eat”. Animals absorb stable isotopes from food and deposit them in body tissues. Feathers, which are most commonly used in migration studies, maintain an isotopic signature from which we can infer the geographic origins of feather molt. This allows individuals to be sampled during the summer to estimate origin of feather growth during the previous winter.

I analyzed isotopes from feathers of six shorebird species: Lesser Yellowlegs, Greater Yellowlegs, Least Sandpipers, Pectoral Sandpipers,Long-billed Dowitchers, and Short-billed Dowitchers. Birds I captured and sampled on Chickaloon had wintered in southern North America and throughout South and Central America. These wintering origins generally mimic the coastal zones of high productivity, which hold major concentrations of shorebirds, and are recognized and protected as Western Hemisphere Shorebird Reserve Network sites. Chickaloon is clearly a noteworthy piece of the migratory network.  

At least 26 species choose Chickaloon as their breeding grounds. The diversity of vegetation provides nesting habitats for many species. The rare and declining Rusty Blackbird nested near a beaver dam. A pair of Wilson’s Phalarope, the first record on the Kenai Peninsula, was photographed along an ephemeral pool on June 7. I found hidden Mew Gull nests on grass-covered islands in ponds and exposed Arctic Tern nests in small grass clumps on seemingly desolate dried mud.

The Chickaloon landscape was significantly altered by the 1964 Earthquake. The estuary subsided 61 cm in the west and 137 cm in the east, leaving behind a tilted landscape that has been uplifting ever since. An analysis of aerial photographs and satellite imagery shows that the area in mud has been increasing since the earthquake, indicating that vegetated areas may be slowly converting to less-productive mud. However, the health of this Alaskan estuary remains uncertain. With the loss of more stable vegetation to early successional species, the earthquake may have initiated a new ecosystem balance and/or changed the rate or stage of succession.

One tern nest was several feet from an airplane track, which was probably made several seasons ago, yet the treads still appeared in the cracked mud. The juxtaposition of three speckled eggs produced after a 20,000-mile migration, nestled next to evidence of a human flight of substantially less, provides hope of continued shared use by wildlife and humans. However, increasing wheeled aircraft landings could hinder recovering vegetation on Chickaloon Flats.

The pulse of life on Chickaloon revolves around the tide cycle. Ephemeral pools are recharged with only the largest and most infrequent of the seasonal tide waters. Patterns of vegetation are largely due to tides, and the resulting salt water and fresh water interactions. Several shorebird species, Arctic Terns, and Mew and Bonaparte’s Gulls forage during receding tides along the sloughs and mudflats. Cook Inlet belugas forage for Coho in the Chickaloon River during high tides. As an estuary, Chickaloon Flats provides predictable tidal habitats and a reliable (compared to interior wetlands) source of abundant resources that shorebirds seek to refuel upon.

On your next drive along Turnagain Arm, I hope you will stop to glass Chickaloon Flats across the waters with a pair of binoculars. Or maybe you will think about the Lesser Yellowlegs flying by — looking for a suitable stopover — and hope it is able to choose Chickaloon. I do. It’s a special place.

 

Sadie Ulman completed her M.S. degree at the University of Delaware this past December. She is now a Research Technician at the Alaska SeaLife Center in Seward. You can find more information about the Kenai National Wildlife Refuge at http://kenai.fws.gov or http://www.facebook.com/kenainationalwildliferefuge.

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