Pacific-slope Flycatcher Life History


Habitat Forests

Pacific-slope Flycatchers breed in shady coniferous and mixed woodlands, especially in places near water where the canopy is partly open. They inhabit second-growth, mature, and old-growth forests, often in ravines or canyons, sometimes nesting on the ground on sides of ravines rather than in vegetation. Among the common conifers in their preferred habitats are Douglas-fir, western hemlock, sitka spruce, incense cedar, western redcedar, sugar pine, ponderosa pine, and redwood, while deciduous trees include big-leaf maple, vine maple, black cottonwood, Pacific madrone, sycamore, poplar, black oak, Garry oak, and tan oak. Understory vegetation in breeding areas is commonly alder, willow, dogwood, currant, wild rose, black hawthorn, and serviceberry. Birds that nest on the Channel Islands also use shady canyons, usually with oaks. Migrants tend to remain within relatively closed habitats as well, and wintering birds in Mexico inhabit both lowland and montane forests, where they also select shaded environments, often near water.

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Food Insects

Pacific-slope Flycatchers eat mostly insects that they capture in flight or else pick from vegetation. They hunt largely from the interior of trees or large shrubs, usually near the middle of the tree, sallying out to catch flying insects beneath the canopy level. Among their known prey items are beetles, bugs, wasps, bees, flies, snakeflies, moths, caterpillars, leafhoppers, and spiders. They also consume berries such as elderberry and blackberry.

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Nest Cavity

The nest is set in trees, large shrubs, cavities, banks, or even in artificial structures; most nests are supported both from below and on one side and are typically 15–20 feet above ground level.

Nest Description

The female builds an elaborate cup nest utilizing spiderweb to bind bark strips, leaves, grass stems, moss, and lichen to the exterior in order to disguise the nest in its setting. She lines the interior with grass and hair, and sometimes with human-made materials like paper, string, or yarn. The nest measures about 4.7 inches across, with the interior cup 2 inches across and 1.1 inches deep.

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Behavior Flycatching

Like other flycatchers of the genus Empidonax, males sing to mark a territory and to attract a mate. They quickly chase any other male that enters the territory (as well as other species of small flycatcher). Territory size ranges from about 2.5 to 8.7 acres, but very few territories have been measured. Territories typically have breaks in the canopy that facilitate foraging and also good nest sites, which sometimes include the sides of ravines or banks, road cuts, or even buildings or bridges. Males sing frequently until they find a mate, then sing mostly at daybreak as nesting begins. No courtship display is known. Pacific-slope Flycatchers appear to be monogamous. Both male and female share incubation duties and feed nestlings.

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Conservation Low Concern

According to the North American Bird Breeding Survey, “Western Flycatcher” (Pacific-slope Flycatcher together with its relative, Cordilleran Flycatcher) have combined populations that appear stable. Survey data from British Columbia showed a long-term annual increase of 1.6% between 1968 and 1996. Partners in Flight estimates a global breeding population of 9.5 million Pacific-slope Flycatchers and rates the species an 11 out of 20 on the Continental Concern Score, indicating a species of low conservation concern.

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Lowther, Peter E., Peter Pyle and Michael A. Patten. (2016). Pacific-slope Flycatcher (Empidonax difficilis), version 3.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

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

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