Tern, tern, tern

Moving from the shores of Lake Superior back to central Wisconsin, with its inland lakes and waterways, means a big change not just in scenery but in the variety of birds and wildlife.

This is especially true of waterfowl, which on the South Shore are numerous and quite varied. Here in the Wausau area we don’t have an inland sea and estuaries, but a riverine environment with all its tributaries and impoundments. So outside of the spring and fall migrations we don’t see as many exciting waterfowl. I for one miss the trumpeter swans that were around all summer up north.

I don’t know if it’s the influence of the lake or not, but we also don’t seem to attract as many sheer oddities as the Bay Area or around the Lake Michigan shoreline. We certainly haven’t seen any birds like fieldfares or crested caracaras — not to mention flamingos or roseate spoonbills — that make national news when they show up in these areas. But we have plenty of water, and with the approach of fall migration we’ll have a peek at some pretty cool birds.

One bird that usually breeds to the east of here along the Door Peninsula and Green Bay is the Caspian tern. They’ve been making occasional appearances around Lake Wausau in the past week or so, and are probably in the process of moving south.

Unlike the sleek graceful common terns that breed along the Bay Area and the North shore, Caspian terns are big lugs. They have a chunky orange beak and tail, without the deep fork seen on the common tern, and are in fact the largest tern on earth (fortunately for them, they’re too big to be hunted down for the purpose of decorating a lady’s hat like the poor common tern). The slim beak and deep tail fork are the best way I can tell a common tern from a Caspian. They also have a gravelly-sounding call that can be heard during migration.

By the way, this tern is named after the Caspian Sea where they are a common species. As a child I was pretty disappointed that they weren’t named after Prince Caspian from the Chronicles of Narnia, but I like to think that they may have accompanied the Dawn Treader on its epic voyage.

But here in the mundane world, Caspian terns are still pretty impressive birds. In addition to their diving and fishing skills, they perform acrobatic dual mating displays on their breeding grounds. I like any mating ritual that involves feeding the female, and male Caspian terns do their part, flying around with a fish to show it off to everyone before presenting it to a favored potential mate.

After they get together, paired terns jointly choose a nesting site and raise young and defend their territory aggressively. Sometimes they attack humans. Caspians usually nest in colonies like other terns, but nest in solitary pairs in some areas. Nests are usually just scrapes on open ground.

Being a Caspian tern parent is a lot of work. That skill you see when terns search, dive for and retrieve fish isn’t inborn. Juveniles are fed by parents for quite a long time after hatching, sometimes on the wintering grounds. But they learn how to hunt and forage in time for their return north the next spring.

Caspian terns are widespread throughout the globe, but are found in discrete, highly localized areas once they’re breeding. In some areas, including Wisconsin, they’re classified as threatened or endangered even as their worldwide populations are generally stable. Like other colony birds, they’re vulnerable to viruses like avian flu; one colony in Washington State was recently wiped out by the flu after conservationists had worked hard to reduce human and predator disturbance there.

These birds have long lives, averaging 12-15 years in the wild, and as a result don’t reproduce quickly (it can take another 15 years to replace one adult lost to illness or predation). Well-meaning humans including bird lovers can spook nesting terns, leaving nests open to gulls and other predators.

So maybe it’s for the best that around here we mostly see them during the migratory period when our presence is less likely to disturb them. I’m glad they’re stopping over on Lake Wausau and hope they can stay safe and healthy.

Sarah Morris is a bird-watcher and outdoorswoman who explores northern Wisconsin from her home base in the town of Gingles. She can be reached at morrisoutside@gmail.com.