Cape May Warbler (Dendroica tigrina)

Size

• The Cape May warbler is a medium-sized wood warbler roughly 13 centimetres (5 inches) long with a weight of about 10 grams (a little under half an ounce).

Appearance

• Distinguishing traits include:
  • Yellow face, neck and belly
  • Dark green upperparts
  • Short tail
• A chestnut ear patch, black-striped underparts and a large white wing patch distinguish the breeding male.
• The female is greyer overall and has two narrow white wing bars.

Voice/Call

• The high-pitched, weak whistle, see-see-see-see, is difficult to hear and is easily confused with the songs of several other songbird species.

• The Cape May warbler is a neotropical migrant that winters primarily in the West Indies and along the east coast of Central America. It breeds throughout the boreal forest of Canada.
• May be found in central and southern Alberta during its migration, but nests in the northern forests, close to the northern and western range limits of the species.
• Local distribution can be strongly influenced by outbreaks of spruce budworm, which this warbler preys upon.

Habitat

• The Cape May warbler seems to demonstrate a consistently strong association with coniferous tree species in old (125+ years) forests, particularly those with spruce or fir canopies.
• Very tall spruce trees that extend above the rest of the forest canopy appear to be a requirement.
• The Cape May warbler avoids recently disturbed areas and is classified as a forest specialist. These factors severely limit the amount of suitable habitat available in Alberta.
• Is highly secretive on its breeding grounds, tending to remain in the upper levels of the forest canopy.

Food

• The species is almost entirely insectivorous during the breeding season, but may add fruit and nectar to its diet on its winter range.
• Diet items in the summer are primarily butterfly and moth larvae and a variety of other small insects including beetles, flies, and ants.
• Spruce budworm is a major food item for this warbler. Forest tent caterpillars are also preyed upon during outbreaks of these insects.

When Active

• Arrives in Alberta in mid- to late May and migrates south in late August through late September.
• Is diurnal, or active during the day.

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, concealed near the trunk high in the tree.
• Five or six eggs are laid, and are incubated by the female alone for 12 to 13 days. Larger clutches may be laid during periods of high food supply.

Growth Process

• Fledglings probably depart the nest after 10 or 11 days.

Status

The Cape May warbler are classified as Sensitive in the current General Status of Alberta Wild Species report. See:

• General Status of Alberta Wild Species

Also see the Status of the Cape May warbler in Alberta report at:

• Detailed Status: Birds

Issues

• The main threat to the Cape May warbler is the loss and degradation of its breeding habitat because of resource extraction and agricultural expansion.
• Forestry activities cause habitat loss and fragmentation, particularly of older and coniferous-dominated forests.
• Short rotation lengths (time interval between successive harvests) and even-aged stand management do not allow forests to develop that are as old and as structurally varied as the Cape May warbler requires.
• Roads and seismic lines from oil and gas development often do not regenerate back to forest and may contribute to habitat loss as much as forestry. These impacts are worsened by habitat loss and alteration within this species’ wintering range and along migration routes.

Current management

• Under Alberta’s Wildlife Act, the Cape May warbler is designated as a non-game animal. It is illegal to kill or harass individuals or disturb their nests at any time of the year.
• There are currently no management efforts that target the Cape May warbler specifically. However, a few research projects in Alberta have recently focused on conifer-dominated habitats at both the stand and landscape levels.
• 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 Cape May warbler will be critical to lessen their impact on this species.