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The Cormorant Monitoring and Management Program was established in 2021 to determine the number of double-crested cormorants in the Bonnyville area and assess possible impacts of cormorant activity on nearby lake fisheries.

You can help by sending us the location and size of cormorant colonies and foraging (feeding) groups when you observe them within the Bonnyville monitoring and management area.

Program update

Extensive field activities ran from May to October in 2021 and 2022. Activities included the following:

  • Aerial surveys

    Aerial surveys were conducted in 2021 on all lakes within 60 km of Bonnyville to determine cormorant colony locations. Colonies were identified on:

    • Frog Lake
    • Lower Mann Lake
    • Muriel Lake
    • Upper Therien Lake

    No colony was found on Moose Lake.

  • Stationary cormorant surveys

    Stationary cormorant surveys were conducted at various locations on lakes in the Bonnyville area to determine:

    • cormorant movements
    • cormorant numbers
    • foraging areas
    • loafing areas

    Most cormorant activity is observed during spring and fall migration, as Bonnyville area lakes offer important stopover sites for migrating species.

  • In-person colony visits

    In-person colony visits were made to the Muriel, Frog, Lower Mann, and Upper Therien Lake colonies for cormorant diet collection and nest counts.

    Nest count surveys indicate that nest numbers were slightly lower in 2022 than in 2021 and remained lower than historical levels. Nesting habitat is limited due to water levels and available nesting substrate.

    Boluses (regurgitations) were analyzed to determine what was eaten. Diet analysis of these boluses indicate cormorants feed on a wide range of species, including:

    • Brook stickleback
    • Fathead minnow
    • Spottail shiner
    • White sucker
    • Yellow perch
  • Trail cameras

    Trail cameras were placed on colonies to monitor colony development and cormorant activity.

    Cameras indicate cormorants are focused on tending nests during the breeding season and only occasionally leave to forage. Minimizing disturbance to nesting cormorants is critical for limiting colony abandonment and reducing cormorant foraging events.

    Several co-nesting species were observed on cormorant colonies, including:

    • American white pelican
    • California gull
    • Common tern
    • Herring gull
  • Oiling cormorant eggs

    Oiling cormorant eggs on Muriel and Frog Lake colonies with non-toxic mineral oil was done in 2021 and 2022 to humanely reduce cormorant population sizes in the Bonnyville area over time by preventing the eggs from hatching.

  • Cormorant banding

    Juvenile (young of the year) cormorants were banded on colonies in 2021 and 2022 to examine life history and population trends.

    You can help by reporting band sightings to:

    • Bonnyville Environment and Protected Areas office
      Phone: 780-826-3142
  • Cormorant capture and satellite transmitters

    Adult cormorants from Muriel and Frog Lake colonies were captured and outfitted with satellite GPS transmitters in the spring of 2022. GPS transmitters actively monitor seasonal patterns in cormorant habitat use, including:

    • foraging locations
    • loafing locations
    • local movements
    • migration routes
  • Disease monitoring

    Colonies in the study area were closely monitored for disease outbreaks in cormorants.

    In 2022, Highly Pathogenic Avian Influenza (HPAI) was confirmed in cormorants at all colonies in the study area. Juvenile mortality rates of up to 50% were confirmed within studied colonies, based on recovery of bands applied to juvenile cormorants.

    Updated information about avian influenza in birds can be viewed at:

  • Fish community assessment

    Fish community assessments were conducted in 2021 and 2022 to assess fish communities at:

    • Frog Lake
    • Kehewin Lake.
    • Moose Lake
    • Muriel Lake

    Reports of the fall index netting surveys can be viewed at:

    Additional summer sampling was conducted in 2022 to assess fish communities at:

    • Lower and Upper Mann Lakes
    • Lower and Upper Therien Lakes
    • Vincent Lake

    Small-bodied fish species including fathead minnow and brook stickleback were identified in all lakes assessed.

Program activities

  • Determining cormorant numbers in the Bonnyville area.
  • Completing movement surveys to determine where cormorants are coming from and where they are feeding.
  • Collecting and analyzing cormorant diet samples to determine what the birds are feeding on.
  • Identifying other birds that co-nest with cormorants, inventorying and implementing mitigation measures to prevent disturbance to these species.
  • Managing cormorants through egg oiling to reduce the population sizes in the area.
  • Completing fish community assessments on waterbodies in the Moose Lake area to determine number and size of fish and any population trends.

Get involved


If you would like to learn more about the Cormorant Monitoring and Management Program, contact:
Email: [email protected]

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