Sunday, December 18, 2011

White-throated Sparrows

I'd say this is an adult tan-morph White-throat based on The Sibley Guide to Birds, page 494.

White-throated Sparrows begin returning in October.  They spend the summer across much of Canada and the North Country, but for some of them, this is far enough south to endure the winter.  Many more go as far as the Gulf and Southern States.  A few western birds hug the Pacific coast in winter.

In the fall, it’s hard to find a good rendition of their song, likened to “Old Sam Peabody, Peabody, Peabody” (hence the nickname “Peabody-bird”).  Perhaps these are young birds, but they have until spring to get it right.  Of course if you’re a Canadian resident, they sing “pure sweet Canada-Canada-Canada.”  Up there it’s known as the Canada sparrow.

Likely a first-winter White-throated Sparrow in December (in an ornamental Serbian Blue Spruce) - © Dave Spier

As adults, this species comes in two genetically-based color races (a.k.a. forms, morphs, or phases) known as white and tan.  Adult "white-morph" birds have high-contrast black-and-white racing stripes on the crown, yellow lores (the area between the eye and bill) and bright-white throats.  The adult "tan" race or version has brown and tan (or beige) head stripes, dull-yellow lores and a dull-white or light gray throat.  The differences have nothing to do with age or gender or geographic distribution as I understand it.  Both types are found mixed in the same population, a situation biologists refer to as polymorphism, or “many forms.”  That said, after the fall molt, the variation is less pronounced in their winter plumage.  To confuse matters, first-winter White-throats resemble the tan race, with lower-contrast head markings and a more-pronounced lateral throat stripe, a.k.a. malar-edge stripe or simply malar stripe.  Many field guides describe "bird topography" with illustrations of various field marks and their names.  In The Sibley Guide (the large, nationwide version), it begins on page 15, with the White-throated Sparrow as the example on page 16.

There are also behavioral differences.  White-morph males are more aggressive while tan females are better care givers.  Tan males and white females fall in the middle.  Ninety percent of the time, one color phase mates with its opposite and it is believed this balances their behavior characteristics.  After the young fledge from the nest, the brood is divided into two groups and each parent cares for only half of the fledglings.

White-throated Sparrows often associate with Dark-eyed Juncos, another type of sparrow.  Both species are ground feeders and at my house they clean up the sunflower seed dropped by the goldfinches, chickadees and other birds above them.  (With sunflower seed getting so expensive [about $25 per 50-pound bag, up from $11 a few years ago], I’ve taken some old metal garbage cans that rusted through on the bottoms, turned them upside down and placed screened tray feeders on top to catch the falling seed.  It used to pile up on the ground faster than squirrels, chipmunks, doves and other ground feeders could clean it up, and then the seed would mold and I’ve have to throw it away.  The screened trays allow precipitation to drain through on milder days, and the birds have a second chance to eat the seed.)

On rare occasions, White-throated Sparrows and juncos have been known to mate and hybridize.  [Off topic, we saw a pure-white junco when we were in Shenandoah National Park early in October.  It was hanging out with other juncos and a flock of Chipping Sparrows on their way south.]

During the summer, White-throated Sparrows consume high-protein insects, but the rest of the year they switch to a vegetarian diet consisting mostly of fallen seeds.  In the wild, they find their food by scratching through dead leaves and grass.  They also eat the fruits of dogwoods, cedars and spicebush.  These native shrubs and trees are plentiful at the Montezuma Audubon Center (MAC), but the sparrows have plenty of competition from thrushes and other berry-loving birds in the fall.  (The Audubon center also hosts a flock of American Tree Sparrows that over-winter in the walnut-grove thickets and brush piles.)   

White-throated Sparrows might be confused with White-crowned Sparrows which are also gray-breasted but lack the yellow lores and usually lack the white-throat.  In the fall, young white-crown’s resemble the color of tan-phase white-throat’s but have what I call a “butch-cut” or slight crest toward the back of the head.  Most of the white-crown’s are long-gone, having migrated farther south; they pass through about two weeks ahead of the white-throat’s.

A few White-throated Sparrows will stay here through the winter, but more return on their way north in the spring.  They stop for a few weeks in April and sing their characteristic song, well refined by then, before continuing north.

High-contrast, white-morph White-throated Sparrow in April with black and white "racing" stripes on the crown. - © Dave Spier

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