Wilsonia canadensis
Canada warbler

Wood warblers solely inhabit the Western hemisphere. Wilsonia canadensis (Canada warblers) breed in the southern boreal forest and in a large portion of southeastern Canada in the Nearctic region and migrates during the spring and fall to their South American winter range in the Neotropical region.

Canada warblers have a diverse range that includes both North and South America at various times during the year. Canada warblers breed in the southern part of the boreal region in North America, from the southeastern Yukon territory, northeastern portion of British Columbia, and parts of northern Alberta across southern Canada as far east as Nova Scotia down to central Minnesota, New York and New England. Canada warblers also breed in the Great Lakes region. The range of Canada warblers extends south in areas of higher elevation through the Appalachian Mountains.

It has been so far determined that Canada warblers only winter in the northern region of South America in the Andes Mountains and in the region to the east of the Andes.

“Accidental” occurrences of Wilsonia canadensis have been recorded in Greenland and Iceland. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Wood Warblers' World", 1984; "Comprehensive Guide to selected species of: Birds of the Boreal Forest - Canada Warbler (Wilsonia canadensis)", 2007; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008)

Canada warblers utilize a mixed woodland habitat. They are found nesting in areas that contain nearly-mature tree stands and an abundance of wet forest floor-cover and understory. Canada warblers will often inhabit areas at higher elevations, near open water. The eastern slopes of mountains where the forest composition is significantly deciduous are preferred. They are found at elevations ranging from 457 to 2500 m. In areas of lower elevation, they reside in bogs, clearings, woodland edges, and open areas created by human disturbance. This species has been found to show preference to mossy areas and it nests near wet habitats. Moss-covered stumps within a foot of water have been noted as extremely favorable nesting spots for Canada warblers.

Canada warblers also occur in riparian shrub forest on slopes, in deep ravines rich with hemlocks, moss-covered boulders and rhododendron thickets. Wilsonia canadensis has also been recorded nesting in more exposed situations, such as in and around birch roots covered with moss and dead leaves, or under bank overhangs of streams. This species chooses very fine, delicate materials with which to construct its nest, so moss is often a key habitat component.

In their wintering range, Canada warblers are found in mature cloud rainforests as well as some coffee plantations and agricultural areas. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Wood Warblers' World", 1984; "Comprehensive Guide to selected species of: Birds of the Boreal Forest - Canada Warbler (Wilsonia canadensis)", 2007; "BFL Species Account: Canada Warbler", 2009; Hallworth, et al., 2008; Savignac, 2008)

Canada warblers are bright, vividly colored birds. The species is nicknamed “the necklaced warbler” because of the unique ring of bluish-black markings around an otherwise yellow breast and throat. Canada warblers have no wing bars and have white under-tail coverts. They feature a yellowish-white ring of color around the eye that creates a spectacle-like marking that is very distinguishable. Canada warblers are remarked to always have a surprised look because of these spectacle markings. They have gray backs and matching wings that fade to black around the crown. They are a small warbler, weighing 9.5 to 12.5 g and measuring 12 to 15 cm in length. Their wingspans measure 20 to 22 cm.

Though females are always observed as having significantly less vivid coloring than males, females generally still exhibit at least a faint necklace marking. This color difference between sexes is typical of warblers, as they usually exhibit sexual dimorphism. There is also a wide variation of the necklace pattern that is independent of age differences. This distinct pattern may be considered a unique marking of individuals. Seasonal variation of a male's markings is typical, with the black markings being much less distinct in the fall than in the spring. In winter, the black coloring turns to more of an inky, bluish-dark gray color.

Juveniles are usually a brownish color on their head and upper body parts, with lighter brown coloring on their under-parts. Any markings on juveniles are far less distinct than adults.

Canada warblers are often confused with other wood warbler species. They look similar to Kentucky warblers, which have a similar body color pattern but no “necklace” markings. Kentucky warblers also have a yellow breast and black cheeks similar to Canada warblers. Magnolia warblers are also similar in appearance to Canada warblers. They are also yellow-breasted with black stripes, but have a gray head and are more mottled with less distinct coloration than Canada warblers. ("American Warblers : An Ecological and Behavioral Perspective", 1989; "Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Warblers of the Great Lakes Region & Eastern North America", 2003; "Wood Warblers' World", 1984; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008)

Canada warblers are considered to be socially monogamous, but sometimes extra-pair copulations may occur during breeding season. Individuals will either arrive at the breeding grounds already in a breeding pair or will form breeding pairs quickly upon arrival.

It was previously thought that Canada warblers maintained pair bonds year-round, however there has been research in the winter ranges that showed solitary birds as well as pair-bonded birds. Individuals of this species often return to the same site to nest, and often remain with the same mate year after year. ("BFL Species Account: Canada Warbler", 2009; Savignac, 2008)

Canada warblers have 2 broods a year on average. Canada warblers construct nests in the shape of a loosely built cup, and they are composed of a huge variety of material including grass, bark, leaf matter, moss, pine needles, twigs and animal hair. Canada warblers can make nests in 3 to 5 days using dried leaves and grass, close to the ground and often at the base of tree stumps or in clumps of ferns. Nest size is approximately 2 inches wide (4.5 inches outside diameter, 2.5 inches inside diameter), and 1.5 inches in depth. In the rare event that they re-use a nest, it will only take the birds about a day to make the nest, as they will likely just add more lining using the previously mentioned nest-construction materials. Optimal nesting areas contain dense shrubbery with abundant cover and protection.

Females usually lay 4 to 5 eggs and incubation lasts approximately 12 days. The eggs are creamy white in color with a slightly glossy finish. They are also speckled with brownish dots in a wreath formation. Average fresh-laid egg mass is 1.56 grams and they are 17.33 mm long. All eggs usually hatch within 24 hours once hatching begins, and if not, then the remaining eggs are likely infertile.

Canada warbler young are very dependent on their parents until they leave the nest. When the chicks are born, they have no feathers and their eyes are closed; they have very poor motor skills but are able to lift their heads for food. By day five, the feather sheaths are visibly prominent, and the chicks may start to stand and stretch their legs. It is estimated that the fledglings leave the nest at ten days old, and Canada warbler parents have been observed feeding their young after their departure from the nest. This species uses direct feeding methods and may regurgitate food for the young. Nestling period lasts an average of 8.1 days. Asymmetry is not uncommon in Canada warbler nests as one chick may be up to 2 times the size of another. The chicks remain dependent on their parents for two to three weeks after leaving the nest. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Comprehensive Guide to selected species of: Birds of the Boreal Forest - Canada Warbler (Wilsonia canadensis)", 2007; "BFL Species Account: Canada Warbler", 2009; "Development of a Baby Bird - Quick Reference", 1997; Savignac, 2008)

For Canada warblers, both parents are very invested in rearing their young. When a nesting site has been chosen, they both work on the construction of the nest. Female Canada warblers are known as “close-sitters” and will remain on the nest for a large majority of the incubation period unless intruders are immediately present. Males have been observed exhibiting anticipatory feeding where they bring food to eggs that have not yet hatched. This behavior may increase during the incubation period.

The male is a frequent presence during the entirety of nesting, and both parents clean out the nest once the chicks have hatched, ridding it of any eggshell or embryonic sac waste. Females remove unwanted pest insects from the nest, which tend to accumulate under the young if the nest is left for a relatively extended period of time. Males will often protect the nesting mother and chicks from a close range and feed the chicks often, sometimes 2 times more frequently than females do. The young are fed very frequently, anywhere from once per minute to every 20 minutes. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Wood Warblers' World", 1984; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008)

The maximum recorded age for a Canada warbler is 7 years, 11 months old, and the maximum estimated lifespan is 8 years. (Savignac, 2008)

Canada warblers are very active and alert birds. Most often, Canada warblers hop along low branches, employing various methods of gleaning as foraging techniques. It flies with great agility and capability, even in thick vegetation. Canada warblers' behavior has been referred to as a "cross between American redstarts and true flycatchers" which is a reference to another of their common names, Canada flycatchers.

Canada warblers are considered to be one of the more timid wood warbler species, however these birds have been observed at very close range with their young. They are extremely vocally territorial, especially in the presence of humans. They are also very protective of their nests from humans, and males have been known to chip up to 96 times per minute in protest of human intruders.

Canada warblers can be hostile and territorial during breeding season. These birds space their nests at about 30 m from each other to establish territory.

During migration, Canada warblers are nocturnal and efficient travelers. They have been known to migrate in pairs, and travel an average of 30 miles a day during migration. This species has been recorded migrating in flocks with other species like tufted titmice, American redstarts, and other warblers such as magnolia warblers, black-throated green warblers, blackburnian warblers, black-and-white warbler, bay-breasted warblers, and chestnut-sided warblers. In Panama, they are seen alone or in pairs with other species in small flocks.

Canada warblers have a rapid migration in late spring and early fall. These migrations can be dangerous as they travel along bodies of water, frequent collisions with lighthouses have been historically reported. During spring migration, Canada warblers travel through wet, swampy wooded areas; similar to Wilson's warblers. In the state of Ohio, they have been observed in spice bushes during spring migration.

They are different than other warblers in migratory habits, as Canada warblers are the last to arrive at the breeding area and usually the last to leave. It usually takes this species about 3 weeks to reach its wintering grounds. It stays mostly in the Appalachians during its route. They leave their winter range by March in Peru, Ecuador by early April and they leave Columbia by mid-April. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Warblers of the Great Lakes Region & Eastern North America", 2003; "Wood Warblers' World", 1984; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008)

The average home range of the Canada warbler is 2 hectares. (Savignac, 2008)

Canada warblers have a very distinct song, though it follows no rules and is characteristically irregular and variant in pitch. They have a flight song in addition to a regular song that sounds the same but is generally longer.

The song of Wilsonia canadensis has been described as a rapid, sputtering warble. A common dictation is “chip-chupety swee-ditchety”, or another is “te-widdle-te-widdle-te-widdle-te-wip”. Canada warblers' songs are notoriously difficult to define, thus the variation in interpretations. The song of this species is different from other warblers; it does not have the same buzzing elements of other warblers’ songs, or the same husky notes. Some say it is a similar, longer version of the song of magnolia warblers. The call by both sexes is a “chyup” sound, while their alarm call is “check” or “chip” in a loud, sharp tone.

Canada warblers sing more after it has completed molting than any other wood warbler species.

Like all birds, Canada warblers perceive their environments through visual, auditory, tactile and chemical stimuli. Their plumage differences serve to visually communicate gender, age, and breeding status to other individuals. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Wood Warblers' World", 1984; "Comprehensive Guide to selected species of: Birds of the Boreal Forest - Canada Warbler (Wilsonia canadensis)", 2007; "BFL Species Account: Canada Warbler", 2009)

Canada warblers are excellent foragers and are well-adapted for catching flying insects. They can be found foraging in lower vegetation like shrubs and tree branches, and occasionally on the ground. Canada warblers use red-osier dogwood and young birch when it forages, as well as shrubs, saplings and the inner, entangled branches of trees. This enforces its niche requirements for substantial understory vegetation. It uses flight during foraging and gleaning in foliage while it hops along branches.

In foraging, Canada warblers are similar to magnolia warblers in that they use deciduous and coniferous mixed-wood habitat equally. Others, like black-throated green warblers, may specialize and differ in habitat use throughout their range.

The diet of Canada warblers consists primarily of flying insects which may include mosquitoes, flies, moths and beetles. At one time, 5 locusts and 29 other insects were found in a Canada warbler's stomach in Nebraska. Canada warblers may also eat small (hairless) caterpillars and spiders as well as insect larvae. They feed heavily on spruce budworm during outbreaks, though it is not considered to be a spruce budworm specialist.

Canada warblers have some specialized physical structures and techniques for catching and eating flying insects. They have sensitive bristles surrounding the beak to aid in sensing and catching flying insects. Once a bird has caught its prey, the flying insects are sometimes held in the warbler’s beak and tossed against a tree branch before being eaten. ("American Warblers : An Ecological and Behavioral Perspective", 1989; "Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Comprehensive Guide to selected species of: Birds of the Boreal Forest - Canada Warbler (Wilsonia canadensis)", 2007; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008; Sleep, et al., 2009)

Canada warblers are subject at some stage of maturity to predation by blue jays and milk snakes. Blue jays have been reported as successful predators on Canada warbler nests, while milk snakes are reported predators of fledglings.

If a predator descends on a Canada warbler nest, the female will launch into a dramatic display and feign an injury on the ground, away from the nest. She does this with her wings cocked out and dragging, fluttering around and with feathers fanned and ruffled. Males will also conduct this display.

Females stay on the nest until a predator is within very close range in order to camouflage and protect the eggs. They will also imitate a fledgling on the ground if the eggs are already hatched to distract predators from the actual fledglings in the nest. ("Wood Warblers' World", 1984; "BFL Species Account: Canada Warbler", 2009)

Canada warblers are considered to be territorial during the breeding season; however they can occur in small mixed-species flocks and with other warbler groups during migration and wintering season. In winter habitats these birds utilize such sites as coffee plantations and may positively impact the crops by consuming pest insects.

Canada warbler nests are frequently parasitized by brown-headed cowbirds in areas of habitat overlaps like Saskatchewan, Ontario, New Brunswick, New York, Indiana, Michigan, and Minnesota. It has been reported that some female Canada warblers will accept these parasitic cowbird eggs and later hatch them successfully. Cowbirds will sometimes remove Canada warbler eggs from the nest so that the parasitic eggs receive priority incubation.

As primarily insectivores, Canada warblers likely impact the insect populations they prey upon. ("BFL Species Account: Canada Warbler", 2009; Savignac, 2008)

There are no known positive effects of Canada warblers on humans.

There are no known adverse effects of Canada warblers on humans.

Wilsonia canadensis was once noted as being the most commonly observed warbler in West Virginia during the 1950's, at and above 3000 feet elevation. It once widely populated all mountain regions of West Virginia along with magnolia warblers.

The conservation status of Canada warblers was designated as “threatened” as of April 1998. This means, under the Committee on the Status of Endangered Wildlife In Canada (OSEWIC) definition, that the species may become endangered if limiting factors are not reduced. Canada warblers have low population densities across their range and deforestation has affected their wintering grounds.

Historically, Canada warblers, black-and-white warblers, and American redstarts have shared one of the highest yearly survival rates at 71%, however Canada warblers have experienced a 40% decline overall since 1966. While this species appears to be mildly resilient to disturbances like forestry practices, Canada warblers are more susceptible to the pressures of island biogeography as more habitat fragmentation occurs.

A positive correlation has also been discovered between spruce budworm and Canada warbler populations, suggesting that increases in spruce budworms lead to increases in Canada warbler populations in certain ranges as well.

The Migratory Birds Convention Act 1994 protects Canada warblers including their nests and eggs. Canada warblers have been designated a Highest Priority Landbird under the North American Bird Conservation Initiative, and Partners in Flight has listed Canada warblers as being continentally important. ("American Warblers : An Ecological and Behavioral Perspective", 1989; "Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008; Sleep, et al., 2009)

Canada warblers are most closely related to hooded warblers. They are named as such because one was first seen in Canada by French ornithologist Brisson.

Canada warblers share the genus Wilsonia with only two other species: hooded warblers and Wilson's warblers. It has reportedly hybridized with hooded warblers, mourning warblers and Connecticut warblers.

The French name of Wilsonia canadensis is Paruline du Canada. Canada warblers have also been called Canada flycatchers because of their inherent insect-grabbing abilities. ("Life Histories of North American Wood Warblers - Order Passeriformes", 1953; "Warblers of the Great Lakes Region & Eastern North America", 2003; "BFL Species Account: Canada Warbler", 2009; Savignac, 2008)