National Geographic : 1936 Apr
THE NATIONAL GEOGRAPHIC MAGAZINE ground. In it a wren was busying itself making small punctures in the blue eggs. Robins make their nests and rear their young as far north as the tree limits of Alaska and Labrador. In winter the more northern birds move southward to the Cen tral and especially the Southern States. Robins sometimes safely winter in the North, even in cold, snowy, central and western New York State, living in swamps, thickets, or gullies and feeding on wild berries. Five varieties are recognized-the east ern robin (T. m. migratorius); southern robin (T. m. achrusterus); northwestern robin (T. m. caurinus); western robin (T. m. propinquus); and San Lucas robin (T. m. confinis). Their songs are very similar and their food and nesting habits vary only to the extent that might naturally be expected of a species inhabiting such a wide variety of regions. American robins have been introduced into England and have become locally es tablished there. Olive-backed Thrush (Hylocichla ustulata swainsoni) This little traveler is one of the few spe cies whose journeys twice a year extend over much of the length of the two Amer icas (Color Plate II). In the extremity of its range it makes a round-trip pilgrimage of more than 17,000 miles. The majority of people who look for the olive-backed thrush see it only as a mi grant. In spring in the New York region we expect it to appear during the second week of May and to depart by the last of the month. At that time it is return ing from its winter sojourn in southern Mexico or perhaps even as far south as Patagonia. Some of these long-distance flyers stop to breed in northern New York State or in New England. Others continue north ward to Newfoundland, to the Mackenzie River, or even to the coast of Alaska that looks out over the icy waters of Bering Sea. In autumn I look again for the migrating olive-backs near my home and usually find some of them between the middle of Sep tember and the fifteenth of October. In the Pacific coast country this form is replaced by a subspecies called the russet backed thrush (H. u. ustulata). Gray-cheeked Thrush (Hylocichla minima aliciae) So closely does this species resemble the olive-backed thrush that only a most ex perienced observer may be expected to tell them apart, when perchance they both ap pear in the shrubbery of the lawn or garden during their seasonal visits. The slightly more pronounced eye-ring of the olive back is the most distinctive mark (Color Plate II). The breeding range of the gray-cheeked thrush is a narrow strip of country just be low the northern tree limit, extending from Labrador westward to Alaska and north eastern Siberia. Wood Thrush (Hylocichla mustelina) Some of the thrushes are difficult for the bird student to name with certainty, but the wood thrush stands out as a conspicu ous exception (Color Plate II). Its breast and sides are thickly sprinkled with round black spots, whereas the similar markings on the underparts of the other thrushes are not so noticeable and are more in the nature of short bars or stripes. Furthermore, this is a large thrush, al though smaller than a robin. It is a little more than eight inches long and has a wingspread of 13 inches, being thus about two inches shorter than a robin and three inches smaller as measured from tip to tip of the wings. These birds pass the winter from south ern Mexico to Costa Rica. In the District of Columbia they appear shortly after the middle of April, filling the parks with their music (see text, page 526). After rearing their young they depart southward about the second week in October. Hermit Thrush (Hylocichla guttata) If you come upon a thrush which has a tail noticeably browner than the rest of its plumage, mark it well, for you have seen the famous hermit thrush (see Color Plate II, and text, page 525). A true hermit, the sweetest singer among all the thrushes dwells in deep and some what swampy woods and seems eager to elude the notice of humans who may, per chance, invade its solitudes. Because of the marvelous quality of its music it has been called "American nightingale."