FRIENDS OF EDGEWOOD NATURAL PRESERVE

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A 2003 calendar will show spring arriving on March 21, but for birdwatchers, spring is indicated by bird migration and song. On a cool late January or early February morning in the Park, a Ruby-crowned Kinglet (Regulus calendula), one of only two kinglet species existing in North America, will suddenly decide to sing, and the sleepy, gray woodlands seem to come alive.

Source: http://www.paulnoll.com/Oregon/Birds/

These olive-green-colored birds are common winter visitors, arriving in late September, and departing in March for their breeding grounds in Canada and Alaska.

Known for their loud and rich songs, this kinglet is one of North America’s smallest songbirds and yet, with up to 12 eggs, lays the largest clutch of any songbird its size (4.25”). To me they always appear nervous, with their tails and wings flicking constantly as they hop from branch to branch in search of grubs and insect eggs.

It can easily be confused with its look-alike, the Hutton’s Vireo (Vireo huttoni), a year-round Park resident. Hutton’s Vireos, aptly described as “the spirit of the live oak tree,“ are similar enough in plumage, size, and behavior to the Ruby-crowned Kinglet, that their identification in the field can be quite a challenge. They are the only non-migratory of the 12 vireo species in North America. Unobtrusive, easily overlooked, the Hutton’s is noticed most often by its persistent but insipid two-parted song, which we begin hearing in late winter.

Ruby-crowned Kinglet—Both sexes are olive green-gray on the upperparts, with 2 strong white wing-bars, and a broken white eye-ring. The underparts are a dusky white. The male has a scarlet crown patch that is generally concealed.

Hutton’s Vireo—Distinguished from the superficially similar kinglet by a thicker bill, broader broken eye-ring, and 2 distinct wing bars with the darkest part of the wing between the 2 bars. Also, this bird seems chunky and large-headed.

Both birds move amid foliage and along branches with short hops, often aided by a flick of the wings, the kinglet appearing more active than the vireo. They prefer to move on horizontal branches rather than climbing up or down vertical branches or trunks. Their flights are short bursts of rapid wing beats, mostly within or between trees.

The kinglet and the vireo will often join mixed-species (i.e. chickadees, titmice, juncos, etc.) flocks, and both are extremely social. Vireo pairs can be found at any time of the year, indicating at least some year-round pair bonding. Kinglet bonding appears to be limited to the breeding season.

Both birds feed primarily on arthropods (insects, mites, spiders, etc.), although in the winter months they occasionally supplement their diets with a small amount of vegetable matter. They secure their food by gleaning it from twigs, under bark, or tree trunks. They are also known to hover to hawk insects or to glean prey from the underside of leaves.

Nest size (3-4” high x 2-3” wide) and construction for both birds are similar. Their nests tend to be globular, or sac-like hanging cups, usually well hidden in tree foliage suspended from forks on horizontal twigs. Various combinations of lichens, mosses, fine grasses, moth and spider cocoons, feathers, small leaves are used as construction materials, all held together with spider silk. Loose strands of nest material are woven on either side of the chosen fork. The loose and hanging strands then are woven together at the bottom, creating the general shape of the nest. Next, finer strands are woven in, and when the structure can support the weight, the bird sits in the nest and arranges the bottom and sides with its feet and body. The female kinglet alone builds the nest, whereas both vireo sexes build. Kinglets locate their nests much higher in trees than do vireos.

A kinglet will lay twice as many eggs (10-12) as the vireo, but the incubation period for both is about the same (14 days), and the young of both remain in their nests for approximately 16 days.

The kinglet has an astonishingly loud and rich song that starts out sounding like a motor chugging to life, and then morphs into a series of chewy-chewy-chewy-chewys. The typical song pattern of the vireo, on the other hand, is monotonous and unmusical. Their calls aren’t much better in that they have a hoarse, scolding quality about them. Vireo songs are delivered from late January through August. They are fairly silent during the remaining months except for an occasional call.

Unpaired male kinglets appear to sing more often than paired birds. Occasionally males sing in flight between singing perches and, remarkably, males can sing while flutter-gleaning for insects and even while consuming prey.

Since male kinglets sing frequently during migration, winter month Park visitors have the opportunity to enjoy their rich, melodious sounds, especially in February and March as they contemplate their departure for breeding grounds to the North.

The Birds of North America: Jeff N. Davis ; No 189, 1995

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