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Olive-sided Flycatcher Life History


Open Woodlands

Olive-sided Flycatchers breed mostly in the boreal forest and in western coniferous forests, from sea level to over 10,000 feet elevation in some parts of the Rockies. Here they are found in forests of spruce, fir, Douglas-fir, hemlock, western redcedar, and tamarack or larch. In southern California and northern Baja California (home to subspecies majorinus), they inhabit mostly pine forest. In all nesting areas, they use openings or edges in the forest and are rarely found in deep, closed forest—look for them in meadows, rivers and streams, partially logged areas, recent burns, beaver ponds, bogs, and muskegs. These areas often have dead or dying trees, which provide exposed perches for singing, foraging, and watching for predators and rivals. Nesting sites near water also provide a great abundance of aerial insects, their chief food. In the easternmost edges of their range, Olive-sided Flycatchers sometimes nest in small towns or on farms, even in apple orchards. In southwestern British Columbia, they occur in stands of Garry oak, which is an increasingly endangered habitat there. On migration, they can show up in almost any habitat with trees, but are more likely to be seen in semi-open forested areas along waterways or bodies of water, with at least a few dead trees present. On the wintering grounds in Central and South America, Olive-sided Flycatchers use forest with gaps and edges as well, in both lowland and highland forest. Water appears to be a less important component of nonbreeding habitat, but scattered tall trees with snags are almost always present.

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Olive-sided Flycatchers eat flying insects, most of which they capture in flight, including flying ants, wasps, bees, dragonflies, grasshoppers, beetles, moths, and flies. They may occasionally eat fruit (berries) during migration or during the nonbreeding season, as other large flycatchers do, but observations are lacking.

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Nest Placement


As is true of many flycatchers, the female chooses the nest site, but males sometimes participate. Nests are usually on a horizontal branch, well away from the trunk and toward the tip. Nests in the northern and eastern parts of range tend to be lower, while those in the West are higher in the tree. The lowest nest on record was 5 feet off the ground, the highest 197 feet. Most nests are placed in coniferous trees (sometimes in burned, dead conifers), but nests in aspen, willow, oak, sycamore, alder, cottonwood, elm, and locust are also documented.

Nest Description

The nest is a loose, bulky but small cup with a foundation of twigs and rootlets, with a lining of grasses, finer rootlets, lichens, and conifer needles. The outside diameter of the nest is about 4.6 inches, the inside diameter 2.8 inches.

Nesting Facts

Clutch Size:3-4 eggs
Number of Broods:1 brood
Egg Length:0.8-0.9 in (2-2.4 cm)
Egg Width:0.6-0.7 in (1.5-1.7 cm)
Incubation Period:15-19 days
Nestling Period:15-19 days
Egg Description:

Creamy white or buff with ring of brownish spots on large end.

Condition at Hatching:

Hatch naked and helpless.

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Pewees (in the genus Contopus) are active, agile flycatchers; and Olive-sided Flycatchers are the giants of this group, more than twice as heavy as Eastern and Western Wood-Pewees. When chasing a rival or a predator, in flying out to take an insect on the wing, their flight is strong, rapid, and direct, recalling the flight of larger kingbirds. The species is highly territorial, often with large territories—sometimes in excess of 100 acres. Territories often do not abut one another but instead are separated by areas of unsuitable habitat. When courting, males may chase females through the territory and perform a short display flight, which the female may join. Breeding males drive out rival males from the territory in swift aerial chases. Once the rival is expelled, the nesting pair reunites, raising crest feathers, clicking bills, and pumping tails and bodies. The pair bond in this species appears to be strong and can survive failed nestings and renesting attempts. At least two cases are known in which a pair nested in consecutive years. Unlike many Nearctic migrants, wintering Olive-sided Flycatchers in Central and South America also hold and defend territories from others of their species. They are rarely found among mixed-species flocks.

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Olive-sided Flycatcher populations are in decline. According to Partners in Flight, their numbers have fallen by 79% since 1970, with the remaining breeding population estimated at 1.9 million. The species rates a 13 out of 20 on the Continental Concern Score and is on the Yellow Watch List for declining populations. Declines may be due to a loss of wintering habitat. This species takes advantage of high insect numbers and good foraging conditions in recently burned forests, and may be adversely impacted by fire suppression and salvage logging.

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Altman, B and R Sallabanks. (2012). Olive-sided Flycatcher (Contopus cooperi), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

North American Bird Conservation Initiative. (2014). The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, Jr. Ziolkowski, D. J. and W. A. Link. The North American Breeding Bird Survey, results and analysis 1966-2013 (Version 1.30.15). USGS Patuxent Wildlife Research Center (2014b). Available from

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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