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COSEWIC Assessment and Update Status Report on the Ancient Murrelet in Canada

Technical Summary

Synthliboramphus antiquus

Ancient Murrelet
Guillemot à cou blanc

Range of Occurrence in Canada: BC

Extent and Area Information

extent of occurrence (EO)(km2) in Canada
200 000 km2 nonbreeding
30 000 km2 breeding

specify trend (decline, stable, increasing, unknown)

are there extreme fluctuations in EO (> 1 order of magnitude)?

area of occupancy (AO) (km2 (adult feeding range = coastline of existing colonies with a buffer of 20 km; estimated coast line of 300 km)
6 000 km2

specify trend (decline, stable, increasing, unknown)

are there extreme fluctuations in AO (> 1 order magnitude)?

number of extant locations

specify trend in # locations (decline, stable, increasing, unknown)

are there extreme fluctuations in # locations (>1 order of magnitude)?

habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat
Number of colonies remains constant; area of colonies declining where predators present

Population Information

generation time (average age of parents in the population) (indicate years, months, days, etc.)
About 7-8 years

number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values)
512 000

total population trend: specify declining, stable, increasing or unknown trend in number of mature individuals

if decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period)
About 18% from 1980s to 1990s at censused colonies

are there extreme fluctuations in number of mature individuals (> 1 order of magnitude)?

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; exchange between colonies in the Queen Charlotte Islands

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)?
Not applicable

Threats (actual or imminent threats to populations or habitats)

  • Introduced mammalian predators; rats or raccoons (primary threat)
  • Disturbance and habitat destruction
  • Oil exploration
  • Oceanographic changes
  • Competition/impact commercial fisheries

Rescue Effect (immigration from an outside source): Moderate

does species exist elsewhere (in Canada or outside)?

status of the outside population(s)?
Uncertain, but likely declining in Alaska and Asia

is immigration known or possible?

would immigrants be adapted to survive here?

is there sufficient habitat for immigrants here?
Yes, but introduced predators may be limiting available breeding sites

Quantitative Analysis

Not done

Current Status

COSEWIC: Special Concern

Recommended Status and Reasons for Designation

Status: Special Concern
Alpha-numeric code:

Reasons for Designation: This is a ground nesting seabird threatened by mammalian predators that have been introduced to its breeding islands. Predators have been removed from some islands but populations have not increased as a result. About half of the world population nests in the Queen Charlotte Islands, British Columbia; the Canadian population is thought to be declining.

Applicability of Criteria

Criterion A (Declining Total Population):
not applicable; current declines poorly measured and unlikely to be large enough

Criterion B (Small Distribution, and Decline or Fluctuation):
not applicable; distribution too large

Criterion C (Small Total Population Size and Decline):
not applicable; population too large

Criterion D (Very Small Population or Restricted Distribution):
not applicable; population and area of occupancy both too large

Criterion E (Quantitative Analysis):
not done.