OLD WORLD WARBLERS: Sylviidae

PHYSICAL CHARACTERISTICS

Old World warblers encompass a variety of different species, as small as 3.1 inches (8 centimeters) long to as large as 9.8 inches (25 centimeters), weighing from 0.1 to 2 ounces (4 to 56 grams). Many species live eight to twelve years.

All Old World warblers have bristles at the base of thin, pointed bills that help them catch flying insects. The wings of species that migrate are long and pointed, whereas the wings of birds that remain within permanent territories are round and short.

Most of the birds in this family are dully colored in greens, yellows, grays, and browns.

GEOGRAPHIC RANGE

These birds have a wide distribution, including the subarctic, Europe, Asia, Africa, North and South America, Australia, and Pacific islands.

HABITAT

Old World warblers occupy a variety of habitats from arid scrubland to islands in the ocean, and every habitable niche in between, ranging from sea level to as high as several thousand feet (meters). Many species occupy specific levels within a habitat, with one species claiming the higher portions, as in the forest canopy, and others claiming lower regions such as bushes or the forest floor.

DIET

Generally, this family of birds lives on insects and spiders. Some species eat snails and small crustaceans. Others, such as the golden-crowned kinglet and some African species, feed on nectar and sap. Some large reed warblers eat fish and frogs. Young hatchlings eat insects and occasionally berries. Migratory birds change their diets to berries and fruit in order to have enough stored fat for flying long distances.

BEHAVIOR AND REPRODUCTION

Many members of this bird family mate for a single nesting or a season, with some mating for life. Males of some species keep two or more females, maintaining separate nests and young. Serial monogamy (muh-NAH-guh-mee), or mating for a single nesting then finding another mate or mates for other nestings, is quite common. Some males have as many as eleven nestings in a season.

Courtship behavior is equally diverse among Old World warblers. Some males will sing elaborate songs. Others will dance, displaying a variety of postures. Still others build nests for show and bring objects as gifts to females.

Old World warblers create nearly every shape and type of nest imaginable. There are cup-shaped nests, domed nests, and round balls that are built from all kinds of plant materials, including moss, lichen, twigs, and grasses. Some nests are built on the ground, some in bushes, and others in trees as high as 80 feet (26 meters). Nests are wedged into the forks of branches or tucked into crevices in walls. Some are hung from vines or leaves. Tailorbirds actually sew their nests. The female punctures leaves with her bill and threads grasses through the holes, even knotting the ends so the nests don't unravel. Both sexes of some species build nests. Females alone will build nests among species whose males have more than one mate.

Females lay one to twelve eggs and incubate them, or sit on them until they are hatched, alone. Males of a few species share this duty. The eggs remain in the nest for ten to twenty-one days and are fed by their parents for one to four more weeks. The young have no feathers at birth.

MIXED FLOCK MIGRATION

The blue-gray gnatcatcher migrates in large mixed flocks of many different species of birds. Though different species, they all prefer forested regions. They stop over in forest edge habitats where there is an abundant variety of food for the diverse flock and adequate protection from predators.

Some Old World warblers forage with many different species in large groups. Others will only feed with their own family group or with their mates.

Some species spy insects from a perch and swoop down on them. Other species stand on the ground and scoop up insects. A few species will either scratch through the litter on the forest floor or use their wings to move the leaves about. Kemp's longbill will poke its bill into dead wood found on the ground.

Old World warblers are a vocally diverse family. Nearly all of them have developed song patterns that range from strictly unmusical repetitions to beautiful, complex melodies. Songs are used to mark territory, attract mates, and communicate with family groups. Duets are songs between bonded mates.

OLD WORLD WARBLERS AND PEOPLE

Since Old World warblers are insect eaters, they hold the potential to be effective pest control for farmers and timber producers. Some nectar-eating species may also act as pollinators for cultivated plants.

CONSERVATION STATUS

Several species are threatened, or at high risk of becoming extinct, or dying out. Fifteen species of marsh warbler are at high risk of becoming extinct. These species are experiencing population declines due to their isolation on oceanic islands where their habitats are being reduced.

ZITTING CISTICOLA (Cisticola juncidis): SPECIES ACCOUNTS

Physical characteristics: Also called the fantailed warbler, the fantailed cisticola, and the streaked cisticola, this bird is 3.9 to 4.7 inches (10 to 12 centimeters) long and weighs 0.3 to 0.4 ounces (8 to 12 grams). It has a brown body streaked with black, reddish sides and rump, and a black and white spotted belly. It has a small thin bill, short round wings, and a small tail.

Geographic range: These birds can be found in Spain, North Africa, sub-Saharan Africa, the Mediterranean, India, Southeast Asia, Indonesia, and the north coast of Australia.

Habitat: The zitting cisticola prefers grassy wetlands as well as some cultivated areas, like sugar cane and grain fields.

Diet: This species eats insect larvae (LAR-vee), spiders, and insects, especially grasshoppers and beetles.

Behavior and reproduction: The zitting cisticola takes insects and insect larvae on the ground. It stays in permanent territories but will move away from the nesting regions after the young can fly. Mediterranean populations are migratory.

The song of the zitting cisticola is a string of a sharp "zit" notes emitted in half-second to one-second intervals.

The males of this species are serially monogamous. Males can mate with one to eleven females in a year. Sometimes, some males will mate with many females at the same time.

Male zitting cisticolas build show nests close to the ground and signal to females by singing. The female builds the real nest, a pear-shaped bag, constructed by weaving and sewing plant fibers and spider webs. She lays two to six eggs and incubates them for eleven to fifteen days. The female feeds the young for ten to twenty days until they leave the nest.

Zitting cisticolas and people: There is no special significance to humans.

Conservation status: This species is not considered to be threatened. ∎

BLUE-GRAY GNATCATCHER (Polioptila caerulea): SPECIES ACCOUNTS

Physical characteristics: The blue-gray gnatcatcher measures 4 to 4.5 inches (10.2 to 11.4 centimeters) long and weighs 0.18 to 0.25 ounces (5 to 7 grams). Bearing a long, thin bill, it has a blue-gray back, a white underbelly with buff sides, a buff colored face, and a long upright tail that is white on the outer edges and black on the inside. When the male breeds, it has a black eye ring; otherwise, it is white.

Geographic range: These birds breed throughout the United States except in the Great Plains, and many will winter in the southern United States, Mexico, Honduras, and Cuba. Some permanent populations exist in Mexico and the Bahamas.

Habitat: The blue-gray gnatcatcher lives in the swampy underbrush and thickets of pine and leafy forests. In the western United States, these birds are found in arid scrub and stands of pinyon-juniper. In humid tropical areas, the birds will occupy the vine tangle of rainforest as well as thorn forests, scrub, and clearings.

Diet: This species eats insects and spiders. The blue-gray gnatcatcher finds insects by diving for them from the air to the forest floor or catching them in the air. Sometimes, they will forage while sitting on a perch.

Behavior and reproduction: These birds live alone or in pairs. Among migratory populations, males will stake out territory, singing loudly, well before the females arrive. Their calls are a thin whine. The male's is a series of notes, chips, and whistles.

Birds of this species mate for life. The male brings his mate to a nest that they both build, made in a cup shape from grasses and spider webs, covered with lichen, and situated on high branches of trees or shrubs. The female lays four to five pale blue eggs flecked with brown that are incubated for eleven to fifteen days by both the male and female. When the eggs hatch, only the female feeds them, but both parents will feed them when they leave the nest, usually in ten to fifteen days.

Blue-gray gnatcatchers and people: Blue-gray gnatcatchers have no special significance to humans.

Conservation status: This species is not considered to be threatened. ∎

ARCTIC WARBLER (Phylloscopus borealis): SPECIES ACCOUNTS

Physical characteristics: The Arctic warbler is 4.1 to 5.1 inches long (10.4 to 13 centimeters) and weighs 0.3 to 0.5 ounces (8 to 15 grams). It has an olive-green back, yellowish white belly, a dark eye line, and straw-colored legs. Its wings are long with two white bars on them.

Geographic range: This species is found in Alaska, Scandinavia, Japan, and the northern regions of Europe and Asia. It winters in Southeast Asia.

Habitat: Arctic warblers live mainly in deciduous forests in the North and in taiga, or subarctic wet evergreen forests. They will winter in rainforest, gardens, woodlands, and mangroves.

Diet: These birds eat insects, especially mosquitoes, and larvae.

Behavior and reproduction: The Arctic warbler finds insects and larvae in leaves, high above the ground. A very active bird, it darts among trees and will flick its wings and tail when it perches.

These birds prefer to live alone or with a mate. Sometimes, they will gather in small family groups. The male will defend his territory through song and wing twitching displays.

Arctic warblers mate for life. The female builds a dome-shaped nest of dry grasses and hair, with a side entrance on the forest floor. The female then lays five to seven pink-speckled white eggs and incubates them for eleven to thirteen days. Hatchlings stay in the nest for thirteen to fourteen days and are fed by both parents.

Arctic warblers and people: There is no known significance to humans.

Conservation status: This species is not considered to be threatened. ∎

FOR MORE INFORMATION

Books:

Baker, Kevin. Warblers of Europe. Princeton, NJ: Princeton University Press, 1997.

BirdLife International. Threatened Birds of the World. Barcelona and Cambridge, U.K.: Lynx Edicions and BirdLife International, 2000.

Perrins, Christopher. Firefly Encyclopedia of Birds. Richmond Hill, Canada: Firefly Books, 2003.

Shirihai, Hadoram, Gabriel Gargallo, and Andreas J. Helbig. Sylvia Warblers. Princeton, NJ: Princeton University Press, 2001.

Weidensaul, Scott. Birds (National Audubon Society First Field Guides). New York: Scholastic Trade, 1998.

Periodicals:

Rodewald, P. G., and Margaret C. Brittingham. "Habitat Use and Behavior of Mixed Species Landbird Flocks during Fall Migration." Wilson Bulletin (March 2002): 87–99.