McCown's longspur (Calcarius mccownii) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

McCown’s Longspur
Calcarius mccownii

Species information

The McCown’s Longspur (Calcarius mccownii) is a sparrow-sized bird with a thick bill and a distinctive inverted black “T” pattern on its white tail. No subspecies are recognized.

Distribution

McCown’s Longspurs have a limited breeding range in the arid grassland regions of North America from southeastern Alberta and southwestern Saskatchewan, south through Montana and Wyoming to northcentral Colorado. Disjunct breeding populations also occur in southwestern North Dakota, northcentral South Dakota, and western Nebraska. The breeding range has contracted substantially since 1900 and the McCown's Longspur is extirpated from Minnesota. It winters in the southwestern United States and northwestern Mexico.

Habitat

Typical breeding habitat is arid, sparsely vegetated native grassland with patches of bare ground as provided by shortgrass prairie or heavily grazed mixed-grass prairie. Breeding habitat for McCown's Longspurs has declined over the last century because of conversion of native grasslands to agriculture and other uses, as well as fire suppression. More recently McCown's Longspurs have been found in cultivated fields such as wheat fields and fallow fields that have patches of bare ground.

Biology

McCown’s Longspurs are migratory and males arrive in Alberta and Saskatchewan in late March or early April. Pairs form when the females arrive approximately two weeks later. The nest is constructed in a shallow depression in the ground and typical clutch size is three to four eggs. The chicks hatch after 12 days and are fed by both parents for 10 days in the nest and another three weeks after fledging. Nest predation varies from 30-75% of nests depending on the site, and is heavier on nestlings than on eggs. Flocks form in August and most McCown’s Longspurs have left Canada on southern migration by the end of September. McCown’s Longspurs are seed-eaters during the winter and on migration, and switch to a seed and invertebrate (especially grasshopper) diet during the breeding season.

Population sizes and trends

The Canadian population of McCown's Longspurs is estimated at approximately 375,000 breeding birds (range: 100,000 - 1 million). Long-term trend analyses based on Breeding Bird Survey (BBS) data indicate an overall decline of 98% in McCown's Longspur numbers in Canada since 1968. This decline appears to have slowed over the last decade, however, with BBS and Grassland Bird Monitoring surveys showing neutral trends between 1996 and 2004.

Limiting factors and threats

McCown's Longspurs have a restricted breeding range that has contracted substantially over the past century. Although the rate of habitat loss has slowed in the past decade, native grassland continues to be lost or altered by cultivation, residential acreages, urban encroachment, and resource extraction. Recently, McCown's Longspurs (20-40% of birds) have been found on agricultural lands where their productivity is likely poor and they risk exposure to pesticides.

Special significance of the species

First collected in 1851 by Captain John P. McCown, the McCown's Longspur is endemic to the North American grasslands and coevolved with the grazing ungulates of this region.

Existing protection

McCown's Longspur is listed as imperiled (S2) in North Dakota, Colorado, Wyoming and Montana, vulnerable (S3) in Nebraska and apparently secure (S4) in Alberta and Saskatchewan. The status of McCown's Longspur in South Dakota is unknown. It is protected from hunting and collecting under the Migratory Birds Convention Act of 1994.

COSEWIC History

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 5th 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.

COSEWIC Mandate

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 Membership

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.

Definitions (2006)

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 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)Footnotea
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)Footnoteb
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)Footnotec
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.

 

Canadian Wildlife Service

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

 

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