August 2015

Vol. 43, No. 4

Front Cover: August 2015

Common Yellowthroat by Barry Van Dusen

Once again, Bird Observer offers a painting by the artist who has created many of our covers, Barry Van Dusen. Barry, who lives in Princeton, Massachusetts, is well known in the birding world. Barry has illustrated several nature books and pocket guides, and his articles and paintings have been featured in Birding, Bird Watcher’s Digest, and Yankee Magazine as well as Bird Observer. Barry’s interest in nature subjects began in 1982 with an association with the Massachusetts Audubon Society. He has been influenced by the work of European wildlife artists and has adopted their methodology of direct field sketching. Barry teaches workshops at various locations in Massachusetts. For more information, visit Barry’s website.

Common Yellowthroat

The Common Yellowthroat (Geothlypis trichas) is an abundant warbler of thickets whose wichity-wichity-wichity song is a familiar sound in spring. Males are easily identified by the black mask, which is set off from the olive crown by a band of white. Their upperparts are olive, and their underparts are bright yellow except for the grayish-olive belly, which separates the yellow throat and undertail. Lacking the mask and white band, females are otherwise similar to males but have drabber underparts. In juvenile females, the yellow is muted. Juvenile males have an indistinct mask.

The Common Yellowthroat is a widely distributed species, breeding in all of the United States except Hawaii, and in all of the Canadian Provinces. Most populations are migratory, although there are resident populations in the southeastern United States, California, and Mexico. They winter in Texas, south Florida, and Mexico; in Central America as far south as Panama; and in the Bahamas and Greater Antilles. In Massachusetts the Common Yellowthroat is considered a common to very common breeder and a very common migrant; it is occasional in winter. Migrants arrive in May and leave from late August through September, although a few may linger.

The taxonomic picture of subspecies of the Common Yellowthroat is muddled due to individual variation in size and plumage, winter range overlap between subspecies, and clinal variation where subspecies are in contact. However, 13 subspecies are generally recognized in this widespread species. The subspecies G. t. trichas is found over much of the eastern half of North America. Common Yellowthroats are closely related to other Geothlypis species such as Kentucky Warbler (G. Formosa).

Common Yellowthroats are usually monogamous, but females dally with other males, which may explain the male’s close following (mate guarding) of his mate, a common behavior in the species. They usually produce two broods per season. The male has two songs, a perch song—wichity-wichity-wichity—and a flight song, which is a three-part complex song incorporating part of the perch song. Males sing the perch song during spring migration throughout the breeding cycle. The flight song accompanies tail bobbing and wings quivering while the males ascend up to 30 feet above the ground. The song presumably serves as both territorial advertisement and mate attraction. Territorial defense involves tchat calls, chases, wing and tail flicking, and occasionally grappling. Females may defend their territory against other females.

Common Yellowthroats occupy a variety of habitats with thick vegetation, from wetlands to undergrowth in pine forests—basically any scrub or thicket environment. The female builds the nest, a well-hidden bulky cup of grass, leaves, and other plant materials; it is lined with fine grass. The usual clutch is four creamy eggs blotched with dark colors. Only the female develops a brood patch, and she alone incubates the eggs for the 12 days to hatching and broods the chicks. The male may bring food to the female during incubation. The young are altricial—nearly naked and helpless; their eyes are closed. By day eight post-hatching, the chicks are able to leave the nest and can fly when they are three weeks old. Both parents feed the young for the five weeks to independence.

Common Yellowthroats forage mainly in low vegetation and on the ground, gleaning leaves and bark. They also hover-glean and hawk flying insects. They have even been recorded foraging at army ant swarms in Mexico. Their diet includes spiders and a broad spectrum of insects: adult beetles, flies, moths, ants, termites, wasps, bees, and a variety of insect larvae—almost anything that crawls or flies.

Common Yellowthroats are often heavily parasitized by cowbirds. In one study nearly half of the Yellowthroat nests contained cowbird eggs. But Yellowthroats often build new nest layers over cowbird eggs or abandon a parasitized nest. As nocturnal migrants, Common Yellowthroats are susceptible to tower strikes. Habitat alteration on their wintering ground may be a problem. Breeding Bird Survey data suggest steady or slightly decreasing population numbers, but the vast breeding area of the species plus land-use policies that encourage early successional growth suitable for Common Yellowthroats bode well for these warblers. 

William E. Davis, Jr.

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