Olive-sided flycatcher (Contopus cooperi) COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

The Olive-sided Flycatcher (Contopus cooperi (Swainson), French: Moucherolle à côtés olive) is a medium-sized songbird 18-20 cm in length. Adults are a deep brownish olive-grey above and on the sides and flanks, with white on the throat, centre of breast and belly. The wings are dark with pale, indistinct wing bars, and the bill is stout. The most distinctive features of the Olive-sided Flycatcher are its tendency to conspicuously perch on the top of tall trees or snags while foraging and the song--a loud three-note whistle: Quick, THREE BEERS!.

Distribution

The Olive-sided Flycatcher breeds throughout much of forested Canada and in the western and northeastern United States. Approximately 54% of its breeding range is in Canada. The winter distribution is more restricted, being primarily in Panama and the Andes Mountains from Venezuela to Peru and Bolivia.

Habitat

The Olive-sided Flycatcher is most often associated with open areas containing tall trees or snags for perching. Open areas may be forest openings, forest edges near natural openings (such as rivers, muskeg, bogs or swamps) or human-made openings (such as logged areas), burned forest or open to semi-open mature forest stands. There is evidence that birds nesting in harvested habitats experience significantly lower breeding success than those nesting in natural (e.g. burned) openings. Generally, forest habitat is either coniferous or mixed coniferous. In the boreal forest, suitable habitat is more likely to occur in or near wetland areas.

Biology

Olive-sided Flycatchers arrive on their Canadian breeding areas between April and June but predominantly mid-late May. They are monogamous, with territories generally well spaced. Nests are typically placed in coniferous trees. Average clutch size is three and a single-brood is raised. Nest success is apparently high (approximately 65%), although no information on hatchling or fledgling success is available. Lifespan and survivorship of adults is also unknown. Birds begin fall migration in late July, with most birds travelling to the wintering grounds sometime between mid-August and early September.

Population sizes and trends

Breeding Bird Survey (BBS) data indicate significant and widespread declines in Olive-sided Flycatcher populations throughout North America and in Canada (4.0% annual decline for the period 1968-2006, 3.3% annual decline for the period 1996-2006, total decline over that decade 29%). The checklist-based Étude des populations d’oiseaux du Québec (ÉPOQ) in Quebec has also recorded a decline in the Olive-sided Flycatcher in Quebec. In Ontario, the Ontario Breeding Bird Atlas project has found a 7% decline in breeding range between 1981-1985 and 2001-2005.

Limiting factors and threats

Olive-sided Flycatchers are generally associated with sparse canopy cover, suggesting that they may respond positively to forest management such as timber harvest. Indeed, their abundance is often higher in early to mid-successional stands derived from wildfire or commercial timber harvest. Their continued population declines, despite apparent increases in the amount of suitable potential habitat on the breeding grounds are therefore puzzling. Evidence from the western United States suggests that there is significantly lower nest success in harvested stands compared with fire origin stands. Resolution of the role of forest management in Olive-sided Flycatcher population decline in Canada is hampered by thinly distributed populations.

Habitat alteration and loss on migration and wintering grounds may also be a contributing factor in population declines. Support for this is provided by the consistent population declines across a wide breeding range, whereas non-breeding areas are more geographically restricted. However, there are no data linking declines in a particular breeding location with specific non-breeding populations. There are no monitoring data for the Olive-sided Flycatcher from migration and wintering grounds to assess trends there.

Special significance of the species

The Olive-sided Flycatcher is a widespread Neotropical migrant with a large portion of its breeding range in Canada.

Existing protection or other status designations

The Olive-sided Flycatcher is classified as G4 (apparently secure) globally and in the United States, and N5 (secure) in Canada by NatureServe; provincial NatureServe rankings also range from S4 to S5 (apparently secure to secure) in all provinces except Labrador (S2S3 Imperiled or vulnerable) and Newfoundland (S3S4 Vulnerable or apparently secure). No NatureServe rankings are available for the Northwest Territories or the Yukon. In contrast, the IUCN red book lists the Olive-sided Flycatcher as ‘Near Threatened’, nearly qualifying as ‘Vulnerable” (similar to the COSEWIC Threatened status) when assessed in 2004. The Olive-sided Flycatcher is protected in Canada by the Migratory Birds Convention Act (1994) and by similar pieces of legislation in Mexico and the United States.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Species

Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)

A species that no longer exists.

Extirpated (XT)

A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A species facing imminent extirpation or extinction.

Threatened (T)

A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*

A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)*

A species that has been evaluated and found to be not at risk.

Data Deficient (DD)***

A species for which there is insufficient scientific information to support status designation.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
** Formerly described as “Not In Any Category”, or “No Designation Required.”
*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.