Vesper sparrow (Pooecetes gramineus affinis) COSEWIC assessment and status report: chapter 11

Technical Summary

Pooecetes gramineus affinis

Vesper Sparrow affinis subspecies – Bruant vespéral de la sous-espèce affinis

Range of Occurrence in Canada:
British Columbia

Extent and Area information

Extent of occurrence (EO)(km²)
2,000 km²
specify trend (decline, stable, increasing, unknown):
Decline
are there extreme fluctuations in EO (> 1 order of magnitude)?
No
area of occupancy (AO) (km²)
<1 km²
specify trend (decline, stable, increasing, unknown):
Decline
are there extreme fluctuations in AO (> 1 order magnitude)?
No
number of extant locations:
1
specify trend in # locations (decline, stable, increasing, unknown):
Decline
are there extreme fluctuations in # locations (>1 order of magnitude)?
No
habitat trend:  specify declining, stable, increasing or unknown trend in area, extent or quality of habitat:
Declining extent and quality

Population information

generation time (average age of parents in the population) (indicate years, months, days, etc.):
2-3 years
number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values):
10-20
total population trend:  specify declining, stable, increasing or unknown trend in number of mature individuals:
Probable decline
if decline, % decline over the last/next 10 years or 3
generations, whichever is greater (or specify if for shorter time
period):
unknown
are there extreme fluctuations in number of mature individuals
(> 1 order of magnitude)?
No
is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., < 1 successful migrant / year)?
No
list each population and the number of mature individuals in each:
Not applicable
specify trend in number of populations (decline, stable, increasing, unknown):
Not applicable
are there extreme fluctuations in number of populations
(>1 order of magnitude)?
No

Threats (actual or imminent threats to populations or habitats)

  • Habitat loss and fragmentation from human development
  • Habitat loss from spread of invasive plants
  • Increased human disturbance at remaining habitat
  • Increased predation pressure associated with increasing urbanization
Rescue Effect (immigration from an outside source)
Low
does species exist elsewhere (in Canada or outside)?
Yes
status of the outside population(s)?
Small, declining
is immigration known or possible?
Possible
would immigrants be adapted to survive here?
Yes
is there sufficient habitat for immigrants here?
No

Quantitative Analysis

Not done

Current Status

COSEWIC: Endangered (2006)

British Columbia CDC: Blue-listed

Status and Reasons for Designation

Status:

Endangered

Alpha-numeric code:

  • B1ab(i, ii, iii) +2ab(i, ii, iii);
  • C2a(i, ii);
  • D1

Reasons for Designation: This songbird, a subspecies of the Vesper Sparrow, is found in Canada only in coastal grasslands in the extreme southwestern corner of British Columbia, where it now breeds only at one site with a population of about 5 pairs. The taxon is declining in the United States as well, where it has a restricted distribution in western Washington and Oregon. Habitat loss is the greatest threat, both through direct destruction of habitat for urban development and through invasion by alien plant species.

Applicability of Criteria

Criterion A: (Declining Total Population):  Rate of decline unknown.

Criterion B: (Small Distribution, and Decline or Fluctuation):  Met Endangered B1ab(i,ii,iii)+2ab(i,ii,iii) because of its very small extent of occurrence and area of occupancy - only one breeding site - and decline in the number of sites occupied and quality of habitat.

Criterion C: (Small Total Population Size and Decline):  Met Endangered C2a(i,ii) because of its low breeding population (< 20 birds) and continuing decline of that population. All the birds occur in this one population.

Criterion D: (Very Small Population or Restricted Distribution):  Endangered D1 (<250 individuals)

Criterion E: (Quantitative Analysis):  Not done.

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