Wild Side: Summer tanagers

Spring migration often brings unusual visitors.

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A summer tanager. — USFWS Digital Library

Spring migration is a hit-or-miss proposition for a Vineyard birder. It never brings the sheer volume of birds that fall migration brings, and to a large extent, it takes the unexciting form of the arrival of our normal breeding birds.

But with so many birds in motion across the continent, and weather that is often (like this year) unsettled and occasionally violent, spring migration invariably brings at least a few unusual birds to the Island. Sometimes it’s a startling rarity (for instance, a year ago the Vineyard hosted the first black-whiskered vireo ever recorded north of the Carolinas). More often, it’s a pleasing mix of “regular rarities” — species typically restricted to regions south or west of us, but prone to being driven here by weather or navigation errors.

The characteristic rarity of this season has turned out to be an attractive and interesting species, the summer tanager. Adult male summer tanagers are nearly as gaudy as the more familiar scarlet tanager: red birds, a bit smaller than a robin, and sporting a large, pale beak. More usual on the Vineyard, though, are duller plumages, often immature males that feature greenish feathers with patches of the vibrant red of an adult. In any plumage, the wings on a summer tanager are much less black than they’d appear in the corresponding plumage of a scarlet tanager — a helpful field mark.

While its range extends across the southern tier of states, the summer tanager is fundamentally a bird of the Southeast, from the Gulf states up into Virginia, Ohio, and Indiana. But this species is prone to vagrancy, and especially to “overshooting” — that is, northbound migrants in spring often get caught in southerly winds and end up far north of the usual range for the species. Overshoot summer tanagers occur with some regularity as far north as the Maritime Provinces. “Vineyard Birds II,” that excellent 2007 compendium of Island records compiled by Soo Whiting and Barbara Pesch, describes the species as an “uncommon vagrant” on the Island, which sounds about right: Though not quite annual here, the species is possible at nearly any point in the year.

The first half of May featured a noticeable influx of summer tanagers, with at least four birds turning up at feeding stations around the Island. This behavior is typical: While summer tanagers are largely insectivorous, they are versatile foragers, perfectly capable of digesting seeds. And arriving here exhausted from its long, accidental trip north, a summer tanager regards a feeding station as a welcome source of effortless calories. One bird this spring was described as feeding almost nonstop for 10 hours after it arrived!

Tanagers, summer or otherwise, are also fond of berries and fruit, and vagrant summer tanagers sometimes take advantage of orange halves Island birders often put out to attract orioles. More generally, though, summer tanagers are fond of insects, and in particular they seem to have a penchant for bees and wasps.

The robust bill of a summer tanager can get a firm and crippling grip on even the gnarliest stinging insect. And these birds have the knack of bashing bees and wasps against a branch to subdue them, and often break off the abdomens, which contain the stinger. I’ve watched a summer tanager set up shop around a feral honeybee hive, catching bees, bashing them, and swallowing them one after another like peanuts, still going at it when I got tired of watching.

While exhaustion makes some Island summer tanagers feed in conspicuous spots, more typically this species can be surprisingly hard to see for a bird that is bright red (males) or yellowish-green (females). Like the scarlet tanager, this is a treetop species, often though not always favoring broadleaf trees. In much of its breeding range, the summer tanager is especially associated with riparian woodland.

Males give a song of short, robin-like phrases, expressed with a distinctive, burry tone quality. Sources say the song of a summer tanager is more halting, with longer breaks between the phrases, than the similar song of a scarlet tanager. I suppose that’s true, but the difference can be subtle, and I’m sorry to say that I might dismiss a summer tanager song as a slightly odd song of a scarlet tanager unless I was paying close attention. More distinctive to my ear is the call note of a summer tanager: a clucking “pit-a-tuck!” that sounds like no other bird vocalization I’ve ever encountered.

Despite their fairly regular occurrence on the Vineyard, summer tanagers tend not to stick around. Arriving at our latitude, they must surely know, in some instinctual, birdy way, that they’ve screwed up, and need to work their way back to Dixieland. I hope they succeed. These are beautiful, active, and charismatic birds, and I wish them all the success in the world.