Vireos and Peppershrikes: Vireonidae

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VIREOS AND PEPPERSHRIKES: Vireonidae

BLACK-CAPPED VIREO (Vireo atricapillus): SPECIES ACCOUNTS
RUFOUS-BROWED PEPPERSHRIKE (Cyclarhis gujanensis): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

Vireos and peppershrikes are small, plain-colored songbirds with a somewhat heavy to very heavy, pointed bill that has a small hook at the end. For most species, the wings are either rounded at the end or are more pointed. Their legs are short but strong. Vireos and peppershrikes are commonly olive brown, olive gray, greenish, or yellowish on the upper parts, and white, light gray, yellow, or yellow-washed on the breast and abdomen. A black line runs through the eyes of most species, but sometimes a white strip goes above the eye while in other species a light-colored eye ring is present. A pale wingbar is usually seen. Females and males are colored almost the same. They are 4.0 to 6.25 inches (10 to 16 centimeters) long and weigh between 0.3 and 1.5 ounces (8 and 40 grams).

GEOGRAPHIC RANGE

The family ranges widely over the Americas including most of the continental United States, all but the northern-most parts of Canada, Mexico, and Central America, most of South America including as far south as Uruguay, northern Argentina, and northern Chile.

HABITAT

Vireos and peppershrikes are found in boreal (northern), temperate, and tropical habitats including woodlands, scrublands, and forests. Some prefer the forest canopy (treetops), while others like dense undergrowth, forest edges, or mangroves (tropical evergreen tree of tidal coasts).

DIET

Their diet consists of insects, spiders, and other invertebrates (animals without a backbone) taken from foliage, flowers, bark, and other plant surfaces. Small berries and other fruits are also eaten.

BEHAVIOR AND REPRODUCTION

Vireos and peppershrikes are usually solitary but active birds, but sometimes appear as a breeding pair or family group. During the nonbreeding season, they are sometimes found in foraging flocks of many different species of birds. Their song is heard often, even during the hottest parts of the day when most birds are quiet, and it usually is loud and melodic, but seldom is it considered beautiful. The song generally consists of several repeated phrases. Different species range from about ten to more than 100 song types. Males sing most frequently, being vocal especially during foraging. Males commonly sing while sitting on the nest. Northern species of the birds migrate, while southern species do not. The trip may vary from 100 miles (160 kilometers) to 3,000 miles (4,800 kilometers).

After migration is complete, birds pair up soon after arriving in their spring breeding territory. Males defend the territory with their song. Open, cup-shaped nests are woven from spider and silkworm webbing, grass stems, other plant fibers, lichens, mosses, and feathers. In species where both sexes build the nests, males construct a rough bag, and females make the lining. Birds locate the nest at the fork of a tree branch, usually suspended by the rim from the bark. The nests are usually located close to the ground or high in the forest canopy.

Females lay two to five whitish to speckled or spotted eggs of various colors. Both females and males perform incubation and caring for the young. The incubation period (time it takes to sit on and warm the eggs before hatching) is usually twelve to fourteen days, and the nestling period (time necessary to take care of young unable to leave nest) is usually nine to eleven days. Fledglings cannot fly well when first leaving the nest, but are good at running along branches and within shrubs. Both parents feed them for about three weeks after leaving the nest. Migratory species usually have two to three clutches (group of eggs hatched together) each year.

VIREOS, PEPPERSHRIKES, AND PEOPLE

Vireos and peppershrikes have no special relationship with people.

CONSERVATION STATUS

One species is listed as Critically Endangered, facing an extremely high risk of extinction, dying out; one species is listed as Endangered, facing a very high risk of extinction; one species is listed as Vulnerable, facing a high risk of extinction; two species are listed as Near Threatened, in danger of becoming threatened with extinction. In all cases, the species are at risk due to loss of habitat as a result of converting native lands to agriculture, thinning out or elimination of forests due to logging, and other detrimental human activities.

BLACK-CAPPED VIREO (Vireo atricapillus): SPECIES ACCOUNTS

Physical characteristics: Black-capped vireos are small vireos with olive-colored upperparts. Males have white under parts, yellow wash beneath the wings, yellowish-white wing-bars, reddish eyes, a blackish bill, a glossy black head, and blue-gray legs and feet. They also have white eye-rings that look like broken eyeglasses. Females are similar except for a slate gray to bluish gray head, white eye-rings, pale lemon-yellow wing bars, buffy white under parts, and yellowish wash on the sides and flanks. Juvenile females have plumage that is more buff-colored. Adults are about 4.5 inches (12 centimeters) long, with a wingspan of about 8 inches (20.3 centimeters) and a weight of about 0.3 ounces (8.5 grams).

Geographic range: During cold months, black-capped vireos are found on the west coast of Mexico. During the warm months when the birds breed, they are located in parts of Texas, New Mexico, Oklahoma, Missouri, and north-central Mexico.

Habitat: Black-capped vireos inhabit open, grassy woodlands that contain clumps of shrubs and trees, especially oak scrublands and dense low thickets. Within that environment, they are usually found around low-lying vegetation.

Diet: They feed mostly on invertebrates such as insects, their larvae (LAR-vee; active immature insects), and eggs, taken from the deep cover among leaves of trees and shrubs. Other food sources are small spiders, small fruits, and berries.

Behavior and reproduction: Black-capped vireos are solitary birds. They migrate short distances between breeding and nonbreeding seasons, often going southwest, wintering along the western coast of Mexico. The birds defend breeding territories. Their song is a hurried string of husky-sounding two- or three-note phrases that is repeated slowly, such as "grrtzeepididid, prididzeegrrt . . . " Their call is a "ji-dit" or "tsidik."

The birds are monogamous (muh-NAH-guh-mus; having one mate). Males court females with fluttering display flights. The male then sings a courtship song, often with the spreading of his wings. The mating pair builds a cup-shaped nest that is made of twigs, bark, and leaves, surrounded with silk and lined with fine grasses. The nest hangs down from a branch fork of a shrub or low tree, about 1 to 15 feet (0.3 to 4.6 meters) off the ground in scrub oak or other short deciduous trees. Females lay three to four white, unmarked eggs. The incubation period is fourteen to nineteen days, which is shared by male (alternating with female during the day) and female (during the night). Both birds feed the young. Two broods are produced each year.

Black-capped vireos and people: There is no known significant relationship between people and black-capped vireos.

Conservation status: Black-capped vireos are not listed as threatened internationally, however, some populations face habitat loss from mining, agriculture, flood-control projects, and reservoir construction. Because of these problems, the U.S. Fish and Wildlife Service placed the bird on the U.S. Endangered Species List. Black-capped vireos are also hurt by cowbirds, which often threaten the birds especially during the breeding season. Efforts in Texas and Oklahoma are underway to trap and remove cowbirds and restrict human activities from areas where black-capped vireos have been most hurt. ∎

RUFOUS-BROWED PEPPERSHRIKE (Cyclarhis gujanensis): SPECIES ACCOUNTS

Physical characteristics: Rufous-browed peppershrikes have a somewhat heavy body, large head, and heavy bill. The back is dark olive-green, chest and flanks are yellow, the belly is white, and the top of head is gray with a broad rufous (reddish) stripe over the eyes. Males and females look alike. They are 5.5 to 6.0 inches (14 to 15 centimeters) long.

Geographic range: They are widely found in Central America from southeastern Mexico to Panama, and in parts of South America as far south as central Argentina (but are not found around most of the area affected by the Amazon River).

Habitat: Their habitat consists of both dry and moist evergreen forest borders, scrublands, gallery and secondary forests, and clearings with trees. The birds are found at altitudes up to 9,200 feet (2,800 meters).

Diet: The birds feed on insects, caterpillars, and other invertebrates found on foliage, flowers, and tree limbs. They also eat small fruits.

Behavior and reproduction: Rufous-browed peppershrikes move about in trees with sluggish movements. They usually stay in the thicker parts of the foliage, so are more often heard, rather than seen. The birds do not migrate, but do defend their breeding territory. Their song is a repeated, musical phrase that is sung year-long. The type of song differs depending on individual birds, and where they are located in their range.

The birds stay together throughout the year. They build cup-shaped, thin-walled nests from grasses, which hang from a fork of a high tree branch. Both the male and female incubate the eggs and feed the young.

Rufous-browed peppershrikes and people: There is no known significant relationship between people and rufous-browed peppershrikes.

Conservation status: Rufous-browed peppershrikes are not threatened. ∎