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Flight Lines: Boreal migrant a treat for area birders

Cape May warblers can occasionally be found along the bark of trees where the birds have a habit of sipping oozing sap. Keith Corliss / West Fargo Pioneer

I wonder just how many residents of the Red River Valley have ever heard of a place called Cape May, New Jersey. Not a lot I'd say. Of those that have, I would venture to guess a good portion consists of bird watchers. One reason being it's the location of a well known migrant hawk watching site. The place is also eponymously applied to a boldly colored small bird which happens to migrate through our area, the Cape May warbler (Dendroica tigrina).

There is simply something magical about warblers. I suppose it has everything to do with the group's vast array of colorations representing perhaps a taste of the tropics, something those of us in the upper Midwest rarely encounter. Most warblers in fact, winter in the tropical areas of the Caribbean or Central and South America, including the Cape May warbler.

Every year about the beginning of May, there is an excited stirring among the area's birders. Anticipation for the warbler migration can be invigorating. Ultimately it begins with a trickle; the yellow-rumped warblers appear then the orange-crowned warblers. Soon after, palm warblers are seen along with black-and-whites. Around the middle of the month there begins a two-week period of furious activity as 20-some warbler species will be seen in the area, among them the Cape May.

Cape May warblers are intricately associated with spruce trees in the boreal forests of Canada and the U.S. where the birds nest. Spruce budworms make up the main source of food for these birds so population numbers fluctuate annually depending on the abundance of their insect prey.

It's easier to identify Cape May warblers than it is to describe them. Its Latin species name - tigrina - means striped like a tiger. But that only covers its breast and upper back. Spring males sport black caps over yellow faces but with bright chestnut cheeks and black eyelines. Mostly green, the birds' upper back is heavily streaked in black. Yellow patches above and below its tail are also evident and help with identification along with a very wide white wing bar. Females lack the black cap, chestnut cheek patch, and generally appear more muted.

Forget hearing these boreal critters if you've lost any high frequency hearing. The song of the Cape May warbler is a high thin "seet, seet, seet, seet."

My father often comments about the lack of warblers at his feeders in South Dakota. I have to remind him that warblers, for the most part, are insectivorous and so won't be seen eating seeds from bird feeders. Instead, observers usually have to focus attention higher in trees. Of the very few warblers which may give your feeders a visit, though, the Cape May is one of them. That is, if you offer some fruit or nectar. Unique among their family, Cape May warblers possess a curled semi-tubular tongue used to sip nectar from flowers.

So frustrating, particularly for beginners, is a typical warbler's habit of flitting about at the uppermost branches of tall trees, offering meager unsatisfying glimpses of birdlife. A dart here, a flutter there--after a time necks are sore from staring straight up at tiny five-inch busybodies buried in clusters of leaves. Luckily, though, with Cape May warblers, we get a break. The birds have a curious habit of feeding on oozing sap which quite often brings them down to quite low levels along the bark of trees, particularly those which have been drilled by sapsuckers. A welcome treat for achy-necked bird-watchers is watching a Cape May warbler clinging to a tree not 10 feet away.

A number of New World warblers are named after places, including the Cape May. That's because the type specimen first described by early ornithologist Alexander Wilson (as in Wilson's warbler) was collected at the cape. Oddly, the bird was not found again there for over 100 years.

Of the 24 warbler species I've seen so far this spring, only four will stay and nest in the area. The rest are making their way farther north, not to be seen again until the fall. Cape Mays will be gone shortly but to see them on nesting territory a person need only travel as far as northern Minnesota.