Wildlife Profile


Hooded Warbler (Wilsonia citrinaI)
by Mark Johns

  Wild Facts about the Hooded Warbler

This small but striking songbird breeds in southern Canada and the eastern United States. The Hooded Warbler seems to prefer shaded habitats, and closely associates with understory components of southeastern forests. Perhaps related to this less well-lit habitat type is the size of this warbler’s eyes. They are among the largest among warblers breeding in the United States, and stand out boldly on its yellow face. Part of its scientific name, citrina, refers to its dazzling yellow color. The adult males have a distinctive black hood and maintain their plumage coloration year-round. Of interest is the fact that on the wintering grounds these birds maintain distinct feeding territories. Individuals segregate by sex during winter, with males usually found in mature forest and females in scrubby habitats. Males have individually distinct songs and have been shown to differentiate between specific rival’s songs from year to year. The Hooded Warbler is declining in only a few parts of its breeding range, and in the east is increasing according to Breeding Bird Survey data.

History and Status

On the breeding grounds, this bird typically inhabits mixed hardwood forests in the north and cypress-gum swamps in the south, but in North Carolina favors moist deciduous woods with a rather diverse understory. It is considered to be a forest-interior species but is also found in smaller woodlots, and near gaps and edges in larger forest patches. It is a neotropical migrant that winters in southern Mexico, Central America and parts of the Caribbean. Neotropical (New World) migratory birds breed during summer in temperate North America, migrating north each spring from wintering areas, then fly back south to spend the bulk of the year in Mexico, Central or South America, or the Caribbean.

Highest densities are generally found with more extensive shrub layer and larger areas of continuous forest according to the Breeding Bird Survey (BBS). BBS shows a non-significant increase in population numbers on a continental basis, with a significant increase in the eastern part of this bird’s range over the last 30 years.

Description

This species is sexually dimorphic in plumage color throughout the year. Adult males are olive green above, bright yellow below, with a black hood and throat. The forehead and cheeks are bright yellow. Females are also olive green above and bright yellow below, with varying degrees of black around the crown or throat. Some older females may look a lot like males, but their hood is never as complete or extensive.

Habitat and Habits

The Hooded Warbler inhabits a variety of forested habitats on the breeding grounds. Typically, territories usually include small clearings or gaps where a thick understory provides nest sites. It is a nocturnal migrant, and during winter utilizes brushy fields, shrubby areas, as well as second growth and mature forest.

Sexes show distinct segregation by habitat on the winter range. Individuals are also strongly territorial during winter. Males are most likely found in mature forest and females in scrub, second growth and disturbed habitats. Habitat segregation is thought to result from male dominance over females. Experiments with hand-raised birds and field data indicate each sex has innate habitat preferences, and that verticality of vegetation may serve as a cue for habitat selection. This winter habitat segregation was first detected in Hooded Warbler and also is now known to occur in other neotropical migrants such as American Redstart, Northern Parula and Black-throated Blue Warbler.

Males defend nesting and feeding territories, and most attract a single mate. However some males remain unmated and some have two females nesting on their territory at the same time. Extra-pair matings are a common and important component of this mating system. DNA fingerprinting studies have shown that about one-third of the females produce offspring fathered by a neighboring male. A mating system such as this is typical of most long-distance migrant songbirds and may influence habitat selection that would avoid small woodlots where there are fewer chances for extra-pair matings.

Females choose nest sites and build the nest. Most nest sites are located within the shrub layer of forest patches and often near edges of distinct shrub patches. Nests are usually close to the ground in saplings or shrubs and are an open cup of woven plant parts. The outside of parts of the nest is often wrapped with dead leaves and leaf skeletons that give it a camouflaged appearance of a clump of dead leaves.

The main food is small insects, spiders and other small arthropods. On the wintering grounds, birds typically forage lower in the canopy on down to the ground. Males and females may forage at different heights on the breeding grounds, with breeding males usually found feeding at the highest parts of the canopy. Food is usually captured by hawking, hovering at the leaf and gleaning.

Range and Distribution

This is a bird breeding in southernmost Canada and the eastern United States that winter primarily in Central America. It is found throughout North Carolina as a breeder, usually in moist deciduous woodlands. There are rare records for birds lingering into winter, but most birds are gone from our area by the end of October.

People Interactions

Some birds likely collide with structures such as TV towers or buildings since this species is a nocturnal migrant. Little information exists on the effects of pesticides or other toxics on this species. Hooded Warblers are considered "area-sensitive", which means they are usually found in larger tracts of mature forest on their breeding grounds. Like many other area-sensitive forest songbirds, this species has nesting habitat availability reduced by forest fragmentation, and likely has additional negative effects added by nest parasites and predators. Deforestation has impacted parts of the winter range. Males prefer forested habitat but will also occupy shrub and disturbed habitat that is usually occupied by females and immature males. Deforestation could force mature males into other habitats, potentially displacing females and shifting the sex ratio in favor of males.

Suggested Readings

Peterson Field Guides: Warblers, by Dunn and Garrett, 1997, Houghton Mifflin Co.
The Ecology of Migrant Birds, by Rappole, 1995, Smithsonian Press


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