Horned lark, strigata subspecies COSEWIC assessment and status report: chapter 2
COSEWIC Executive Summary
Species information
The Horned Lark strigata subspecies (Eremophila alpestris strigata) is the rarest subspecies of Horned Lark in Canada. It is a small, brown, yellow, and white bird with a distinctive black facial mask and black headband, which extends in the male into tiny feather tufts or “horns”.
Distribution
Eremophila alpestris strigata occurs only in the coastal plains of southwestern British Columbia, Washington and Oregon. In British Columbia, its distribution is restricted to the lower Fraser River valley from the mouth of the Fraser River east to Chilliwack, and southeastern Vancouver Island.
Habitat
Eremophila alpestris strigata occurs in short-grass habitats and areas with bare ground. In British Columbia, suitable sites may include natural areas such as spits, estuaries, sand dunes, and Garry oak ecosystems, as well as anthropomorphically modified areas such as pastures, airports, playing fields, and roadsides.
Biology
Eremophila alpestris strigata nests on the ground where its clutch of three to five eggs is placed next to a tuft of vegetation or small object. The breeding season in British Columbia was reported from early April to late August. It feeds primarily on seeds during non-breeding seasons but invertebrates are also consumed during spring and summer, and are a food source for nestlings. Birds may have migrated south to Washington and Oregon for the winter but a few may have remained in British Columbia in some years. Horned Larks are known to tolerate grazing and irregular operation of machines, but tend to nest away from urban landscapes and may suffer nest destruction from mowing or other vehicular traffic.
Population sizes and trends
The Canadian population is estimated to be between one and five birds. Only one bird was recorded during grassland surveys in 2002, and the subspecies was previously considered extirpated on Vancouver Island and extremely scarce in the lower Fraser River valley. Eremophila alpestris strigata was never known to be abundant in British Columbia. Populations likely peaked in the 1920s and 1930s, then declined through the 1980s to the point of extirpation. About 300-500 birds are thought to occur in Washington and Oregon. Trends in all jurisdictions are downward.
Limiting factors and threats
The primary limiting factor for this subspecies is the lack and decline of suitable breeding habitat. Habitats have become increasingly developed for human activities such as housing, recreation, agriculture and light industry. Continuing development pressures will, in the future, likely alienate most of the remaining habitat. Small areas of natural habitat also have increased pressure for use by humans, which is not compatible with ground-nesting birds such as Horned Larks.
Improved dyking of the Fraser delta has reduced the amount of sparsely vegetated sandy shoreline along the edges of the Fraser River. Invasions of exotic plants have alienated much of the remaining field, Garry oak and sand dune ecosystems. Increasing use of chemical pesticides, increasing predation pressure from domestic cats and wildlife that is associated with urban areas, and increasing recreational use of open spaces likely affect habitat suitability.
Populations in Washington and Oregon are also declining. Therefore it is becoming increasingly unlikely that there will be a source of dispersing birds to reestablish breeding populations in British Columbia.
Special significance of the species
In Canada, Eremophila alpestris strigata occurs only in southwestern British Columbia where it is one of a small group of vertebrates that are considered to be associated with the rare Garry oak ecosystems. The subspecies appears headed towards extinction, given severe downward population trends in all jurisdictions.
Existing protection or other status designations
Eremophila alpestris strigata is protected from persecution by the Migratory Bird Convention Act, 1994, and the British Columbia Wildlife Act. A few historical breeding sites are protected within regional parks.
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. 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.
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 and include 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 organizations (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership, chaired by the Canadian Museum of Nature), three nonjurisdictional members and the co-chairs of the species specialist and the Aboriginal Traditional Knowledge subcommittees. The committee meets to consider status reports on candidate species.
Definitions (After May 2003)
- Species
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Any indigenous species, subspecies, variety, or geographically or genetically distinct population of wild fauna and flora.
- Extinct (X)
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A species that no longer exists.
- Extirpated (XT)
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A species no longer existing in the wild in Canada, but occurring elsewhere.
- Endangered (E)
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A species facing imminent extirpation or extinction.
- Threatened (T)
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A species likely to become endangered if limiting factors are not reversed.
- Special Concern (SC)*
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A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.
- Not at Risk (NAR)**
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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 Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.
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