Olive-sided Flycatcher

The Olive-sided Flycatcher, Contopus cooperi, is a small to medium-sized passerine bird belonging to the Tyrant flycatcher family, Tyrannidae. This agile avian is smaller than an American robin but larger than a sparrow, with a distinctive olive-grey or grey-brownish plumage above, and a striking white mid-breast and throat. The bird's sides are grey, giving the appearance of a vest, particularly noticeable in good lighting or when the feathers are freshly moulted. It has a relatively long bill and wings for its size, and sometimes sports a small crest of raised head feathers. Both sexes are similar in appearance, lacking sexual dimorphism.

Identification Tips

When identifying the Olive-sided Flycatcher, look for its upright perching posture atop dead branches or trees. Its olive tones are most visible in optimal light conditions. The bird's long bill, long wings, and the vest-like grey sides against the white mid-breast are key characteristics to observe.

Habitat

The Olive-sided Flycatcher breeds in open areas or edges of boreal, coniferous, or temperate western forests, often near water and up to elevations of 10,000 feet, such as in the Rockies. It can also be found in urban settings or on farms. During the non-breeding season, it occupies similar habitats, with less dependence on water proximity, and is associated with habitats featuring very tall trees.

Distribution

This migratory species travels vast distances from South to North America to breed during the summer months. Its breeding range extends from California to New Mexico, up to central Alaska, across Canada (excluding most of the Northwest Territories and Nunavut), and into parts of the northeastern United States. In the non-breeding season, it resides mainly in the northern part of South America and some areas of Central America.

Behaviour

Studies have shown that Olive-sided Flycatchers near their nests may fly varying distances, with some males singing only when more than 100 meters away from their nest. Pairs nesting in more open areas tend to travel shorter distances than those deeper in the forest.

Song & Calls

The male Olive-sided Flycatcher's song, used to attract a mate during breeding, is a distinctive "Quick, three beers!" consisting of three successive high-pitched sounds. The first note is shorter and less loud than the following two. Males may also produce growling sounds or squeaks when in conflict with other males. Their most common call is a series of three quick, successive pip sounds.

Breeding

Breeding once per year, the Olive-sided Flycatcher typically lays clutches of 3 to 4 creamy white eggs with brownish spots. The incubation and nestling periods last about 15 to 19 days each. Nests are cup-shaped, built on horizontal branches of coniferous trees, and vary in height depending on the region. Both parents feed the young, with the male defending a large territory around the nest.

Similar Species

The Olive-sided Flycatcher can be confused with other Contopus species such as the Greater Pewee, Western Wood-Pewee, Eastern Wood-Pewee, and the Eastern Phoebe. Key differences include the plain grey breasts of the Greater Pewee, the smaller size of the Wood-Pewees, and the more white underparts of the Eastern Phoebe.

Diet and Feeding

Primarily insectivorous, the Olive-sided Flycatcher employs hawking to capture flying insects like bees, wasps, moths, and beetles. During migration and non-breeding seasons, it may also consume fruit. Parents have been observed consuming their chicks' fecal sacs, possibly as a nutritional supplement.

Conservation status

The Olive-sided Flycatcher is currently classified as "Near Threatened" by the IUCN, with an estimated global population of 1.9 million individuals. The species has experienced a significant decline, estimated at 3% per year, and has decreased by 79% over the past 50 years. In Canada, it is listed as threatened under the Species at Risk Act due to its declining population.

Climate change

Climate change poses a significant threat to the Olive-sided Flycatcher, with studies indicating that habitats with tall trees are crucial for the species' resilience. The bird is expected to prefer valleys, lowlands, and flatter areas that can support wetlands or streams.

Threats

Human disturbances and road proximity negatively impact populations, particularly in Canadian national parks. Loss of wintering habitat is a major concern, as is the decline in flying insect populations due to insecticide use. The species may also be affected by wildfire suppression techniques, salvage logging, and collisions with communication towers.