September 11, 2008

Smorgasborg is Shifting to South


The weather is cooling. The kids are studying. The harvest is roaring. The shotguns are shining.

These iconic images proclaim that autumn is soon upon us. For some of our fellow creatures, however, that is hardly a news flash.

Incredible as it may seem, many arctic-nesting shorebirds began their "fall" migration in early July.

For most such species, adult females were the first to depart the top of the world, leaving their mates to shepherd the tiny puffball chicks through the hazards of tundra and taiga living - not that those shorebird fathers were paragons of familial dedication.

They began their own southbound movements several days later. The abandoned and often still flightless chicks were forced to figure out how to navigate between the Arctic Circle and tropical wintering locations all on their own.

Although that parenting strategy may strike us as a bit heartless, there is no arguing success.

Shorebirds have colonized most surface habitats on planet Earth, and have diversified into a bewildering variety of species.

That diversity, coupled with the aforementioned gender- and age- segregated migration, means that we here in North Dakota are treated to an ever-changing shorebird smorgasbord, stretched out between mid- July and early November.

The feast this year has been particularly rich and scrumptious.

The fun began in early July when the vanguard of adult female least sandpipers arrived at local wetlands. The most happening spot I found was Long Lake National Wildlife Refuge.

Long Lake is subdivided into three long pools, the third of which stretches far to the north, then far, far to the east. This year that mighty pool was starved for water, creating ideal conditions for migrating sandpipers and plovers.

Sensing that there might be something spectacular happening there, I visited the refuge again in mid-July, but was disappointed to find that there was basically no water, and very few shorebirds present.

Refuge staff later explained that I had been duped by the North Dakota wind.

Long Lake pool number three had such shallow water, and such an extraordinarily smooth bottom, that during days of southwest winds, what water there was simply was blown north, then east, around the corner, and out of sight.

When the wind shifted direction a few days later, one of my young daughters and I tried again.

We were greeted with an extraordinary vision. There were several thousand acres of shallow to very, very shallow water surrounded by hundreds and hundreds of acres of wet mud, bounded by vast stretches of dry mud. Because different shorebird species prefer different water depths, there was something for everyone, and everyone it seemed, had gotten the message.

Two or three stilt sandpiper were feeding within every square foot of shallow water. Thousands upon thousands of dowitchers crowded among them, while American avocets patrolled the slightly deeper zones.

In the very shallow areas, least and semipalmated sandpipers feed in small flocks, while the wet mud was carpeted with the largest concentration of Baird's sandpipers I have ever seen.

At the peak there were at least 200,000 shorebirds present, a phenomenal number for an inland location.

Each subsequent visit brought new wonders, as different shorebird age and gender classes, let alone different shorebird species, pulsed through.

The first trip, the big news was the stilt sandpipers and my young daughter becoming entangled with a thistle patch after I sent her on a potential short-cut (once I saw her difficulties, I took the long way around).

The second trip we saw both piping and semipalmated plovers and my daughter learned the hard way about prickly lettuce, cockleburs, and horseflies (noting her distress I quickly donned chaps, headnet, and repellent for myself).

And so it went, through ruddy turnstones, sanderlings, and buff- breasted sandpipers, as well as knee-deep alkali mud, deer flies, scorching heat, and poison ivy.

The great shorebird smorgasbord is now slowing down. I have just returned from Long Lake National Wildlife Refuge, where I encountered but a few thousand birds.

The highlights included newly arrived black-bellied plovers and American golden-plovers, but I had to enjoy them alone, as my daughter said she would rather stay home and do the laundry. Go figure.

(Dan Svingen is a biologist for the Dakota Prairie Grasslands in Bismarck. )
