Olive-sided Flycatcher
By Andy McCormick
PC: John James Audubon (Olive-sided Flycatcher)
Scientific Name: Contopus cooperi
Length 7.5 in
Wingspan 13 in
Weight 1.1 oz
AOU Band code OSFL
This bird of summer is often seems in need of refreshment and loudly calls out QUICK, THREE BEERS. Its indulgence makes it a favorite of birders and provides a readily identifiable bird song. The song is given from a prominent perch at the edge of, or in the middle of, a swampy area at the edge of a forest where flies and bees will be plentiful. The Olive-sided Flycatcher feeds by sallying out from its high perch to catch insects and returning to the same or close-by perch.
The Olive-sided is similar in behavior to other pewees in the genus Contopus, short footed, from the Greek kontos, short and pous, foot. The reference is to the relatively short tarsi of this genus (Holloway). It shares the genus with the Western Wood Pewee C. sordidulus, a slightly smaller bird with similar flycatching behavior, but lacking the clear vest look. The Olive-sided species name is in honor of the zoologist William Cooper, 1798-1864, former director of the New York Lyceum of Natural History.
The bird is olive-brown above with olive-gray sides and white throat, chest and belly giving the bird a distinctive appearance of wearing an unbuttoned vest (Altman & Sallabanks). It also has white tufts on the sides of the rump which are often hidden by the wings. It has a dark and blocky head with an equally heavy bill. From a distance the bird looks all gray.
The Olive-sided breeds primarily in conifers. Both male and female live up to the family name Tyrannidae, Tyrant Flycatchers, by fiercely defending their nest, which is built on a horizontal branch well out from the trunk. Usually three pinkish-buff eggs with dark spots are deposited. Incubation is by the female only for a little over two weeks, and the young, fed by both parents, take flight in three weeks.
The conservation record of the Olive-sided Flycatcher is a difficult one. It has been extirpated (wiped out) in the early part of the 20th Century from southern New England, Maryland, Tennessee and the Carolinas and Sequoia National Park in California. Breeding Bird Survey analysis shows a decrease of nearly 74% throughout its historical range between 1966 and 2005 (Wells). Some suspect that changes to habitat on the wintering grounds may be causing declines. Others suggest that insecticide spraying has reduced the abundance of its primary prey.
The Olive-sided does well in post-fire areas and forest fire suppression may have negatively affected this species. Ironically, tree harvesting, which leaves some snags and thus mimics burned areas, has attracted Olive-sided Flycatchers. But a theory has been offered that these areas can be an “ecological trap” which will attract birds to breed, but then expose them to more predators, such as squirrels and corvids, leading to increasing nest failures.
The Olive-sided is a long-distance migrant that is more numerous in Western North America. It uses the Pacific Flyway to migrate to the Andes Mountains stretching from Venezuela to Columbia, where it is most common. Scientists need to “develop a baseline inventory of Olive-sided Flycatcher breeding and wintering populations, habitat needs…and factors responsible for continuing populations declines” (Wells).