Canada Warbler Life History

Habitat

Habitat Forests

Canada Warblers breed in mixed conifer and deciduous forest with a shrubby and mossy understory often near water. They frequent forest slopes filled with rhododendrons in the southern Appalachian Mountains, aspen and popular forests in Canada, and forested wetlands in the central part of their range. During migration they forage and rest in shrubby areas in parks, woodlots, and along forest edges. They winter in forests with dense undergrowth, forest edges, shade-coffee plantations, and scrubby fields across northern South America between 3,200 and 6,000 feet.

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Food

Food Insects

Canada Warblers eat many types of insects and spiders. They quickly hop between branches picking insects from understory vegetation in a flurry of activity. They also grab flying insects in the air, a foraging strategy called flycatching or hawking.

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Nesting

Nest Placement

Nest Ground

Females select a spot on or near the ground within areas of dense shrubs, ferns, or rhododendrons. The nesting spot is often in a small depression made by an upturned tree root, a rotting stump, or a clump of moss.

Nest Description

Females weave together grass, leaves, plant down, moss, and strips of bark to make a bulky and loosely constructed cup-shaped nest. They line the nest with animal hair, rootlets, and fine grasses. Females build a nest in 3–5 days.

Nesting Facts
Clutch Size:2-6 eggs
Number of Broods:1 brood
Egg Length:0.6-0.8 in (1.6-1.9 cm)
Egg Width:0.5-0.6 in (1.2-1.4 cm)
Incubation Period:11-12 days
Nestling Period:8 days
Egg Description:

Creamy speckled with small brown dots and blotches.

Condition at Hatching:

Naked with eyes closed.

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Behavior

Behavior Foliage Gleaner

Canada Warblers quickly hop between understory trees and shrubs often while flicking their wings and cocking their tail. They tend to stay in the lower canopy and understory, foraging alone or near their mate. During migration and on the wintering grounds though, they flock with other species including Wilson's Warblers, Tufted Titmice, and American Redstarts. Males and females frequently return to the same breeding area year after year to breed. They may form a monogamous bond during the breeding season, but many also seek out extra-pair copulations. Brown-headed Cowbirds frequently lay eggs in Canada Warbler nests. This nest parasitism by cowbirds reduces the survival of nestling Canada Warblers. If a female is disturbed while on the nest by a predator or human, she may feign wing injury to distract the predator, chip loudly, or become agitated.

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Conservation

Conservation Declining

Canada Warblers are relatively uncommon as their populations declined by 62% between 1970 and 2014, according to Partners in Flight. They are a Yellow Watch List species with a declining population and a Continental Concern Score of 14 out of 20. The current estimated global breeding population is 3 million. Partners in Flight estimated in 2015 that if the current rate of decline continues, Canada Warblers will lose another half of their remaining population by 2072. Population declines are likely due to changes in forest structure, forest management practices that reduce understory vegetation, and loss of forested wetlands. Extensive browsing of understory vegetation by white-tailed deer has altered the forest understory, eliminating the shrubby component Canada Warblers need for nesting. Logging practices that thin understory vegetation may also reduce nest-site quality.

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Credits

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Lutmerding, J. A. and A. S. Love (2016). Longevity records of North American birds. Version 2016.1. Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Pieplow, N. (2017). Peterson field guide to bird sounds of eastern North America. Houghton Mifflin Harcourt Publishing Company, NY, USA.

Reitsma, Len, Marissa Goodnow, Michael T. Hallworth and Courtney J. Conway. 2009. Canada Warbler (Cardellina canadensis), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

Stephenson, T. and S. Whittle (2013). The Warbler Guide. Princeton University Press, New Jersey, USA. 

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