A Novel Voice of the Boreal Forest

by Kathy Ross

Olive-sided Flycatcher – Photo Credit: Jake Bramante

It was an early spring morning in Glacier Park backcountry. Along with a group of researchers, I stood mesmerized by the drama we were witnessing. In the tall, grassy, wet meadow below us, a gray wolf unrelentingly chased a distraught cow moose. The intense scene was suddenly lightened by the capricious “quick-three-beers” song of an Olive-sided Flycatcher (Contopus cooperi) perched on the snag beside our viewing point. This was my first introduction to this unusual flycatcher song imprinting it forever in my memory.

The Olive-sided Flycatcher is an unfamiliar bird to many folks but once you pick up on the distinctive song, even without an intense experience with which to relate, the emphatic demand for “quick-three- beers” can stick with you. Listen for it as you wander the edges of wet meadows, forest openings or rivers running throughout boreal forests. Also, it is linked closely with fire and other natural disturbances, as long as enough snags and trees are left to provide singing and hunting perches. “It is one of a suite of species that occur at higher densities in burned rather than unburned areas…”(1)

This congener of the pewees is one of the larger flycatchers at around 7.5”. It is large-billed, deep olive-brown with dark sides on breast and flanks, separated by a white patch down the center of the breast. The tail is broad and prominently notched. Like most flycatcher species, it feeds almost entirely on flying insects, with bees, wasps and ants thought to be preferred fare. In typical flycatcher fashion, it makes dashing aerial attacks to catch prey in the air. The Olive-sided uses high exposed perches, mostly snags, returning to the same perch with captured meal. “It is the only North American flycatcher to use this method of hunting exclusively.”(2)

The Olive-sided Flycatcher is one of the latest nesters of all breeding birds in North America. Nesting can occur mid-May to mid-June and even into July. It breeds from Alaska all the way across the northern boreal zone to eastern Canada and northern New England. In the western mountains, it can also be found breeding in Central California, Arizona and New Mexico, with scattered populations turning up in Baja California, southern Nevada mountains, Texas and the eastern mountain ranges.

Females do all of the two-week long incubation of eggs, with males providing food during this time. Together the pair defends the nest aggressively in the event that a hapless squirrel or another intruder might get too close to the nest. Of the 3-4 young of a productive but sometimes later season nest, the fledglings may leave the nest as late as early September. It should be noted, “overall annual productivity of this species is among the lowest of any North American songbird.”(3) An Oregon study found highest nesting success in burn areas and lowest productivity in forest edge nests. Look for nests on the outer ends of the highest conifer branches in clusters of twigs and needles.

The short breeding season coupled with fluctuating climate changes is probably partially responsible for this low productivity. Along with loss of forested habitat in Central and South America, there is a noted decline in this flycatcher species. This significant decline has brought about a conservation status of “near threatened” for this species.

The Olive-sided Flycatcher is one the amazing group of long distance avian migrators. They leave the Boreal forest breeding grounds of Canada or the northern tier US as early as late July, if nesting is unsuccessful, and all have departed by October. According to Skaar’s latest Montana bird distribution map, September is the latest recorded sighting of this flycatcher species in our area or state. The migrating populations usually travel along the western mountains of North America and Mexico. The majority of Olive-sided Flycatchers may winter in Panama or northern Andes of Venezuela but may travel as far south as the forested regions of western Bolivia. The highest densities have been found enjoying the tropical warmth of Columbia.

With the steady decline of this interesting and unique forest songbird, be aware of its presence in our forests. Listen for its distinct song and watch for it on snags, especially near forest edges and wetlands. Encourage the protection of forested habitats, especially on its tropical wintering grounds, to ensure that this distinctive voice of the Boreal forest always remains part of our forest experience.

Sources:  (1)Boreal Songbird Initiative, Guide to Boreal Birds, (2)Cornell Lab of Ornithology, All About Birds, (3) Montana Bird Distribution, 7th Edition