BIRD OF THE WEEK: Dec. 23, 2016
SCIENTIFIC NAME: Cardellina rubrifrons
HABITAT: Breeds in high mountain forests, winters in cloud forests
The Red-faced Warbler is one of only two North American warblers with red plumage; the other is the Painted Redstart, another species of the Mexican border. The Red-faced has colorful plumage year-round, and both sexes look alike, although males are generally brighter than females.
This flashy warbler shares high-altitude forest habitats (sometimes called “sky islands” because they are isolated mountaintops surrounded by much drier habitat) with other neotropical migrants such as Olive-sided Flycatcher and Thick-billed Parrot. Red-faced Warblers are sensitive to habitat loss on both breeding and wintering grounds.
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The Red-faced Warbler is one of the least-studied North American warblers, as its range barely reaches the United States. Partners in Flight estimates that only around 36 percent of the population breeds in the U.S. This population is found in the highlands, or sky islands, of Arizona and New Mexico. The rest are found in Mexico.
Red-faced Warblers prefer to forage in trees with dense foliage, particularly in conifers, where they glean a variety of insects, especially caterpillars, from the outer branches. This species also hover-gleans like a flycatcher to catch insects.
During the summer, males tend to feed higher in the trees than females, pausing to sing as they forage.
The Red-faced Warbler builds its cup-shaped nest in a hollow on the ground. The nest site is often on a slope in the open or at the base of a woody plant. Sometimes the nest site has an overhang provided by a plant stem, log, or rock, which helps to conceal and protect the nest.
The nest itself, built by the female, is made of bark, leaves, or pine needles with a lining of grasses or animal hair. Only the female incubates the eggs, but both parents feed the young when they hatch.
During breeding season, pairs of Red-faced Warblers maintain an all-purpose territory where both male and female feed. The male establishes, defends, and advertises the territory; the female also defends the territory against other females.
Although this species appears to be typically monogamous (a single pair maintains and defends a territory), the birds engage in high rates of “extra-pair” activity. Neighboring males often sneak onto established territories to copulate with females of other pairs, and females occasionally leave their territory seeking other males. In fact, almost three-quarters of nests contain a young bird fathered by a male other than the territory owner.
Extra-pair copulation, which provides genetic benefits to a female's clutch, has been found to be common among this species and many other birds.
Like other neotropical migrants of the American Southwest, including Elf Owl and Lucy's Warbler, the Red-faced Warbler benefits from habitat conservation and restoration on both sides of the U.S. and Mexican border. Conservation of the Red-faced Warbler's “sky island” breeding habitat, as well as stopover and wintering areas, is needed to keep this bird's populations intact.
ABC's work with partners to “bring back the birds” is a large-scale conservation strategy that can help slow declines of the Red-faced Warbler and other unique migratory birds, from the Western Tanager to the Scarlet Tanager.
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