Golden-winged warbler (Vermivora chrysoptera) COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

The Golden-winged Warbler (Vermivora chrysoptera Linnaeus, Paruline à ailes dorées) is a small (9-11 g) wood warbler.  Both sexes are grey with yellow wing patches and crown; males have black masks and bibs.

Distribution

The Golden-winged Warbler breeds in the northeastern United States and southern Ontario, as well as in extreme southwestern Québec, southern Manitoba and southeastern Saskatchewan. The species winters in Central America and northern South America including central Guatemala and northern Honduras, southward to northern and western Venezuela, and western Colombia.

Habitat

On the breeding grounds, Golden-winged Warblers are found in areas of early successional scrub surrounded by mature forests. They are found in dry uplands, swamp forests and marshes. Examples of some preferred habitat areas include hydro/utility right-of-ways, field edges, recently logged areas, beaver marshes and areas that are burned or intermittently farmed.

On the wintering grounds Golden-winged Warblers may be found at high elevations (1,500-3,000 m) in various types of open woodland habitats, pine-oak and scrub. However, they have also been described as lowland dwellers by some. Within the preferred habitat types, the species is found primarily in canopies, within gaps or along edges of forests, and in tall second growth.

Biology

Breeding pairs raise only one brood per year with an average clutch size of 4.75 nestlings per nest (range = 2-6) in Ontario. Subsequent breeding attempts are common in the case of nest failure, especially when failure occurs near the start of the breeding season. Approximately 55% of nests fledge at least one young, while 45% of nests have been known to fail (N=103 nests in Ontario) due to predation and/or abandonment. 

The species is known to be strictly insectivorous during the breeding season. The preferred diet consists mainly of tortricid moths and their larvae, although other moths and their pupae, other winged insects and spiders are sometimes consumed. Similar feeding habits are also seen on the wintering grounds.

Population sizes and trends

The Golden-winged Warbler has been experiencing population declines for at least 30 years and is currently one of the fastest declining passerine species in North America. In Canada, the species was showing population growth up until 10 years ago, likely because of a northeastward range expansion. Since that time the species has started to disappear from regions in the southernmost portions of Ontario. The northward range expansion is thought to now have stopped in Ontario and Quebec, but continues northwestward into Saskatchewan.

Inconsistencies in reported numbers of Golden-winged Warblers make accurate estimates of population size difficult.  Current best estimates of the global population range from 105,000 to 270,000 breeding pairs.  Breeding Bird Survey (BBS) data suggest approximately 20,000 to 50,000 pairs breed in Canada, approximately 18.5% percent of the global population. The vast majority of these breed in Ontario. In Québec, the population has been estimated to be between 210 and 540 pairs. In Manitoba, where breeding has been taking place since 1932, Breeding Bird Survey data estimate a total population of 105 to 270 pairs. However, results from recent intensive surveys and a remaining abundance of unsurveyed land suggest numbers in Manitoba may be as high as several thousand individuals. In Saskatchewan 19 birds have been reported to date with evidence of probable breeding on one 1:50,000 mapsheet and possible breeding on two other mapsheets.

Limiting factors and threats

On the breeding grounds Golden-winged Warbler declines are associated with a decrease in early successional scrub environments required for breeding, hybridization with the Blue-winged Warbler (V. pinus), and Brown-headed Cowbird (Molothrus ater) parasitism, although great variation is seen in the impact of these factors by location.

Threats associated with migration and wintering ground habitat have not yet been studied directly, but as with most neotropical migrants, they are likely linked to declines in the Golden-winged Warbler.

Special significance of the species

The Golden-winged Warbler has generated a great deal of scientific and public interest over the past 30 years. Field research and citizen science projects have been actively exploring reasons for the species’ decline for at least 15 years. The species has a unique genetic history, being closely allied to only one other species (the Blue-winged Warbler) even though it is currently considered to be one of nine species within the Vermivora genus (one of which, the Bachman’s Warbler, is extinct).  The Golden-winged Warbler can be seen as a representative for many other successional scrub breeding birds that are facing widespread population declines. As such, the conservation of this species will benefit numerous other avian species in Canada.

Existing protection

The Golden-winged Warbler is not federally listed in the United States, although it has designation in 12 states and is currently under federal status assessment in the U.S. to determine whether it warrants protection under the U.S. Endangered Species Act.  In Québec its status is “Likely to be designated as threatened or vulnerable”. The Migratory Bird Treaty Act of 1918 provides protection from taking, killing or possessing the species. NatureServe gives the Golden-winged Warbler a global ranking of G4 (apparently secure – uncommon but not rare).

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^th 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. 

Wildlife Species: A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X): A wildlife species that no longer exists.

Extirpated (XT): A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E): A wildlife species facing imminent extirpation or extinction.

Threatened (T): A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*: A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**: A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***: A category that applies when the available information is insufficient (a) to resolve a species' eligibility for assessment or (b) to permit an assessment of the species' risk of extinction.

*       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. Definition of the (DD) category revised in 2006.

Environment                      Environnement
Canada                             Canada

Canadian Wildlife              Service canadien
Service                             de la faune

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