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Bay-breasted Warbler (Dendroica castanea)

Bay-breasted Warbler


  • The bay-breasted warbler is a small bird, about 14 centimetres (five-and-a-half inches) long and weighing about 13 grams (about half an ounce).


  • Breeding male characteristics include:
    • A chestnut crown, throat and flanks
    • Cream-coloured underparts
    • A black mask
    • A creamy patch on each side of the neck
    • Two white wing bars
  • The female is duller, with only a faint chestnut cap.


  • Song is a weak, extremely high-pitched seee-seese-seese-seee. The call is not distinctive and is difficult for some people to hear.
  • This neotropical migrant winters in Central and South America and breeds across the boreal forest of Canada and in the northeastern United States.
  • It is found in Alberta’s boreal forest and foothills, near the northern and western limits of its range.
  • This warbler is rarely observed during its migration in Alberta, and is uncommon in most areas of the province. Therefore, little is known about its ecology.
Natural History


  • Typical habitat for this species in Alberta is found in mixedwood stands of white spruce and aspen or balsam poplar, but pure coniferous and deciduous forest with conifer understorey can provide suitable habitat.
  • A secretive species, the bay-breasted warbler is often difficult to spot in the wild, as it tends to favour the mid to upper levels of the forest canopy.
  • Bay-breasted warblers have rarely been found in disturbed sites during the breeding season and are considered a forest specialist species.


  • Usually forages at the mid-level of trees for food.
  • Diet items in the summer are primarily butterfly and moth larvae and a variety of other small insects including:
    • ants
    • beetles
    • dragonflies
    • flies
    • grasshoppers
  • The bay-breasted warbler is known to be a major predator of spruce budworm and forest tent caterpillar during outbreaks of these insects.

When Active

  • Individuals are known to arrive in Alberta in mid- to late May and leave for fall migration from mid-August through mid-September.
Reproduction and Growth

Breeding Behaviour

  • Pair formation presumably occurs shortly after arrival on the breeding grounds, and males aggressively attack and chase each other in territorial defence.
  • Nests are most often built in coniferous trees, on a lateral branch away from the main trunk.
  • Five or six eggs are laid, and are incubated by the female alone for 12 to 13 days.
Conservation and Management


The bay-breasted warbler are classified as Sensitive in the current General Status of Alberta Wild Species report. See:

Also see the Status of the Bay-breasted Warbler in Alberta report at:


  • Populations of this fish have decreased over the past few decades due to:

    • Habitat fragmentation and loss, primarily as a result of forestry, oil and gas development and agricultural expansion threaten the breeding habitat of the bay-breasted warbler.
    • Removal of older stands combined with short rotation lengths (time interval between successive harvests) tends to keep forests at younger stages of maturity.
    • Exploration for oil and gas contributes to the loss of habitat and leads to fragmentation of the remaining forest by creating long-term linear disturbances such as roads and cutlines.
    • This loss of habitat quantity and quality has been implicated in the population declines of neotropical songbirds across North America. Similar habitat change affects the wintering grounds of these species.

Current management

  • Under Alberta’s Wildlife Act, the bay-breasted warbler is designated as a non-game animal and it is illegal to kill or harass individuals or disturb their nests at any time of the year.
  • There are no management activities specific to the bay-breasted warbler in Alberta, and detailed information on the population trend and habitat use is lacking.
  • Alberta’s Endangered Species Conservation Committee has recommended the conservation of its habitat through long-term forest management focused on maintaining populations that are well distributed over the species’ historical range. Modifications to resource extraction activities that currently affect the preferred habitat of the bay-breasted warbler will be critical to lessen their impact on this species.


Page Information

Updated: Jan 8, 2014