Canada Warbler

Wilsonia canadensis

Glen Tepke
  • PARULIDAE
  • Wood Warblers
  • 1.4 million

The Canada Warbler is a little-studied species that typically breeds in cool, moist forests of the United States and Canada. A long annual migration takes it to its wintering grounds in northern South America, where habitat loss is a threat. Habitat degradation and loss on the breeding grounds has also negatively affected populations.

Identification
The distinctive black markings across an otherwise yellow throat and breast gives this warbler the nickname of "Necklaced Warbler." The unmarked back and wings are slate-gray, edging towards black on the crown, and a white eye-ring boldly characterizes the face. The female is similar to the male, though the necklace is less distinct and the face and crown are more olive-gray than black.

The clear, loud song is extremely variable, consisting of a chip note followed by an abrupt, explosive series of short notes that invariably ends with a 3-note phrase, the last one loud and rising in pitch. The song is often described as chip chupety swee-ditchety or chip, suey de swee-dictchety.

Distribution and Population Trends
During the breeding season, the Canada Warbler's range stretches from northeastern British Columbia and northern Alberta across southern Canada to Nova Scotia. This species can be found in many types of forest in central Minnesota, the Great Lakes region, New York, and New England. It is also found at higher elevations in the southern Appalachians, stretching south from New York, through Pennsylvania and New Jersey to western North Carolina and northern Georgia. Canada Warblers breed in a number of Audubon Important Bird Areas including New York's Moose River Plains and Catskill High Peaks IBAs and North Carolina's Roan Mountain IBA.

It winters in northern South America, including Venezuela, Colombia, Ecuador, Peru and northern Brazil.

Canada Warblers are not abundant within most of the breeding distribution, and based on Breeding Bird Survey (BBS) results from 1966 - 2001, populations have declined at rate of 1.9% per year throughout the breeding range. The most severe declines are in the northeastern U.S., perhaps a result of a change in forest structure over the past century. Optimal habitat may have been provided as previously farmed land regenerated to forest, but disappeared as the forest matured and eliminated the understory. Forested wetlands, also suitable for Canada Warbers, have been drained, filled, and developed during the 20th century.

Ecology
Birds leave the wintering grounds between late March and mid-April and arrive on the breeding grounds between mid-May and early June. Important stopover habitats include bushes and vine tangles near the edge of parks, villages, and cities, and thickets of stream and woodland edges, swamps and willow trees.

The Canada Warbler will inhabit many types of forest during the breeding season, primarily coniferous and mixed northern hardwood forests with dense, often wet, undergrowth. They appear to prefer limited ground cover, but high foliage density in the shrub layer. Little is known about territoriality, but the male appears to arrive on the breeding grounds before the female and aggressively defends a territory by singing. The female builds the nest alone, it is usually placed on or just above the ground among ferns, stumps, and fallen logs, or, in the southern part of its range, in rhododendron thickets. Dense nest site cover appears to be important habitat requirement. There is little information about the incubation and nestling periods, but it appears the incubation period is performed only by the female and lasts for about 12 days. During the nestling period, which lasts for about 10 days, both parents feed the nestlings. Fall migration starts in mid-July to late August, the first individuals typically arrive on the wintering grounds by early September.

Their diet consists of flying insects and spiders, captured by flycatching or gleaning prey from both conifers and deciduous trees, or off of the ground.

Threats
Sensitive to forest fragmentation and human disturbance, populations have been apparently negatively affected on both the breeding and wintering grounds due to habitat loss and degradation. Extensive cutting and forest fragmentation in eastern deciduous forests has reduced this bird's breeding habitat. Nest predation is higher in fragmented forests. Populations that breed in the southern Appalachians are particularly vulnerable to habitat loss and degradation from air pollution, especially acid rain, since they only nest in sensitive spruce-fir habitats at high elevations. Loss of coniferous habitat from infestations of the Woolly Adelgid are a major issue in much of the species southern breeding range. Habitat loss on the South American wintering grounds may continue without decreases in human population growths and changes in policies toward habitat conservation.

Conservation
Although little conservation work has been directly focused on the Canada Warbler, much land has been purchased for conservation purposes throughout its range which likely benefits the species. Audubon New York's Forest Biodiversity Stewardship Program is developing landowner outreach and educational materials for how private forest landowners can manage for Canada Warblers and other forest-dependent species through various forestry techniques. To find out more visit: http://ny.audubon.org/FOREST/index.html

Canada Warbler is listed as a priority species in Partners in Flight's Bird Conservation Plan for the Adirondack Mountains, an area where the species reaches some of its highest breeding densities (http://www.partnersinflight.org). One of the objectives of this plan is to ensure the availability enough northern hardwood/mixed forest suitable to support 15,000 - 20,000 breeding pairs of Canada Warbler distributed among 600-700 atlas blocks.

What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Canada Warbler as well as other species. To learn more about the Important Bird Area programs in states with breeding populations of Canada Warbler, and how you can help, visit: http://www.audubon.org/bird/iba/

Support local land trusts, government agencies, and other organizations working to preserve habitat in your area. Contact your state Important Bird Areas coordinator (http://www.audubon.org/bird/iba/state_coords.html) to find out if there are sites in your area important for Canada Warblers that need increased protection.

U.S. National Wildlife Refuges provide essential habitat for Canada Warbler, and a great number of other species throughout the U.S. and its territories. Unfortunately, the refuge system is often under-funded during the U.S. government's budgeting process. To learn more about how you can help gain much needed funding for U.S. National Wildlife Refuges, visit: http://www.audubon.org/campaign/refuge_report/

Audubon and our partners in conservation coordinated the submission of over two million comments to the U.S. Forest Service in support of the Roadless Area Conservation Rule, which would protect habitat for Canada Warbler and many other species. Unfortunately, implementation of the Rule has been stalled and attempts are being made to weaken it. To help in protecting these vital habitats visit: http://www.audubon.org/campaign/latestnews.html#roadless

Information on where Canada Warblers occur and in what numbers is vital to conserving the species. Help in monitoring this and other species by reporting your sightings to eBird. A project of Audubon and the Cornell Lab of Ornithology, eBird is the world's first comprehensive on-line bird monitoring program: http://www.audubon.org/bird/eBird/index.html.

The Cornell Laboratory of Ornithology and the USDA Forest Service coordinate Birds in Forested Landscapes, a citizen-science project that links volunteer birders and professional ornithologists in a study of the habitat requirements of North American forest birds, including Canada Warbler. To learn more about Birds in Forested Landscapes, and how you can participate in the project, visit: http://birds.cornell.edu/bfl/

Audubon is the U.S. representative of the global BirdLife International alliance. Our BirdLife partners in Canada and South America are developing Important Bird Areas programs to identify and conserve critical habitats that support Canada Warblers and many other species. For more information on BirdLife IBA efforts throughout the Americas visit: http://www.birdlife.net/sites/index.cfm

References
Birds in Forested Landscapes Species Account: Canada Warbler (Wilsonia canadensis). Cornell Lab of Ornithology. http://birds.cornell.edu/bfl/speciesaccts/canwar.html

Conway, C.J. 1999. Canada Warber (Wilsonia canadensis). In The Birds of North America, No. 421 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Dunn, J. and K. Garrett. 1997. Peterson Field Guide: Warblers. Houghton Mifflin. New York.