Vancouver Avian Research Centre

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Species: Olive-sided Flycatcher Contopus borealis


With its loud resounding song—quick, THREE BEERS!—and its position of prominence perched atop a large tree or snag, the Olive-sided Flycatcher is one of the most recognizable inhabitants of North America’s coniferous forests.
This flycatcher undergoes one of the longest and most protracted migrations of all nearctic migrants and the longest migration route of any flycatcher breeding in North America.
It winters in Panama and the Andes Mountains of South America.


General: This is a large flycatcher appearing proportionally bull-headed, and short-tailed with a stout bill. Easily identified by large size and “vested” plumage pattern on underparts.
Length 18-20 cm, weight 32-27 g.

Adult Male: Dark patches on either side of white breast and belly are distinctive and often likened to appearance of an unbuttoned vest. Occasionally white patch is also visible along sides or flanks. Dark wings, with only indistinct pale-grayish wing-bars. Adult plumages are similar throughout the year.

Adult female: Sexes are alike in appearance. The sexes are best distinguished in the hand by wing length, which is longer in the males.

Juvenile: The plumage is similar to that of an adult, except the upperparts are more brownish, and the wing-bars are washed buff.

Similar Species: This flycatcher could be potentially confused with similarly sized Greater Pewee. The Greater Pewee is distinguished by fairly uniform colour of under parts (center of breast and belly not pale and thus not contrasting with dark sides and flanks).

Behavior: See the Olive-sided Flycatcher perched conspicuously on tops of trees from which they fly out (sallying) to snatch flying insects, and then return to the same or another prominent perch.

Habitat: It is common in North America’s coniferous forest. It breeds in habitat along forest edges and openings, including burns; natural edges of bogs, marshes, and open water; semi-open forest; and harvested forest with some structure retained. Tall, prominent trees and snags, which serve as singing and foraging perches, and unobstructed air space for foraging, are common features of all nesting habitats.


Olive-sided Flycatchers prey almost exclusively on flying insects, especially bees. Their typical foraging behaviour of “sallying” or “yo-yo flight” has led to this species being described as “the Peregrine of flycatchers”.
This bird is monogamous and produces 3-4 eggs per clutch and 1 clutch per pair per year. Nests are open-cup structures placed at various heights above ground and well out from the trunk of a coniferous tree in a cluster of needles and twigs on a horizontal branch.

Conservation Status:

In the past 30 years this species has experienced significant declines in populations throughout its range, causing it to be listed as a Species of Concern in some areas.

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