Winter: South America, mainly in the Andes from Colombia and Venezuela to southeastern Peru; in small numbers in Central America and southern Mexico, also in Amazonian and southeastern Brazil.
Primarily montane and northern coniferous forests, usually at mid- to high-elevations. Within coniferous forest biome, most often associated with forest openings, forest edges near natural openings (e.g., meadows, bogs, canyons, rivers) or human-made openings (e.g., harvest units), or open to semi-open forest stands. Presence in early successional forest appears dependent on availability of snags or residual live trees for foraging and singing perches. Frequently occurs along wooded shores of streams, lakes, rives, beaver ponds, bogs and muskegs, where natural edge habitat occurs and standing dead trees often are present.
In spite of its very large range, this species occurs in overall low density and is of great conservation concern, because of precipitous population declines in nearly every region. An overall loss of 67% has been noted since 1966. Deforestation in its Andean wintering range is a likely culprit, although understanding this species sensitivity to silvicultural and other land-use practices will be important for conserving future populations.
Male: The Olive-sided Flycatcher is a stout, block-headed, short-tailed bird with a large bill. The back is olive-gray-brown, with similar colored streaked sides. Dull white runs from the throat down the center of the breast to the light belly. Some characterize this underside as an unbuttoned vest. Pure white tufts are sometimes visible on perched birds poking from behind the wings above the rump, and also in front of the wings on the sides (this second set of tufts is not mentioned in most identification guides).
Female: Same as adult male.
Juvenile: Essentially like the adult in color pattern, but darker above and brighter below; upperparts dark brown, brownish-buffy or brownish-white wing bars are distinct.
Song: A sharp, penetrating whistle, whip WEEDEEER, often depicted as quick, three BEERS, though Pacific birds sing a subtly different what peeves yoou with equal emphasis on all syllables.
Call: A low, hard pep pep pep with variations from soft, rapid piw-piw-piw to harder pew, pew to single pep or quip.
Unlike many other flycatcher species that can attack prey by hovering and striking or pouncing on prey on the ground, Olive-sided Flycatchers are restricted almost entirely to sallying for aerial prey. Typically sallies out to snatch a flying insect, then returns to the same or another prominent perch. A passive sit-and-wait predator, remaining perched until prey is sighted, then actively pursues prey, including insects that are often difficult to capture.
Almost exclusively flying insects. Bees, wasps, and flying ants make up a large portion of the diet; also takes flies, moths, grasshoppers and dragonflies. In Alaska, eats Yellow-jacket Wasps.
Behavior and Displays
Male pursues female through territory, making several short, looping display flights near perched female.
Receptive female may fly with male, the birds make shallow, synchronized downward swoops together with 1 bird approximately 3 feet (1 meter) above the other.
Female solicits copulation by landing on branch near male and rapidly fluttering half-open wings.
Male also may reinforce pair bond during incubation by occasionally swooping at a perched female to force her back on nest.
Nest site: Female appears to choose nest site, although some males suggest locations by repeatedly flying to certain branches while female is nearby and bellying down into foliage as if molding lining of a nest. Generally saddled on top of a horizontal branch, well out toward the tip, often where overhanging branch provides some security and protection from weather. Most nests in coniferous trees, although observed in trembling aspen and willow.
Height: Average is 32 feet (10 meters).
Nest: Female constructs a loosely formed, somewhat bulky, shallow and relatively small nest. Foundation and frame mostly twigs and rootlets, also uses arboreal lichens.
Eggs: 3, sometimes 4, creamy white, buff or pale salmon eggs with ring or wreath of spots or small blotches near large end.
Incubation Period: Female incubates for 15-19 days. Male may bring food to female on nest, particularly during early incubation.
Nestling Period: Little known; lasts 3 weeks, typically between 15-19 days.
Fledgling Period: Actual time of departure from nest is difficult to ascertain because nestlings spend time on branches near the nest before their first flight, and some birds return to nest or nest branches after fledging. Some departures, particularly when nestling period is protracted or when other nestling have already departed, are solicited by adults with food.
Broods: Single brooded.
Cowbird Parasitism: Rare host species for Brown-headed Cowbird, possibly due to aggressive defense around nest site.