DUSKY CANADA GEESE & BALD EAGLES

Surveying the effects of predation & environmental changes on a resilient species

Story by Patty Karafotias

Photos by Rhys Marshall

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Evan Standifer finds himself trudging through the Alaganik Slough just outside of Cordova, Alaska, on a weekly basis, conducting surveys of Dusky Canada Geese - a subspecies of geese that breed solely on the Copper River Delta in the summer and migrate south toward Fern Ridge Reservoir, just west of Eugene, Oregon, in the winter months.

 

The 1964 Great Alaska Earthquake, with its epicenter located 12 miles north Prince William Sound, largely affected such aerial species which prompted the current study of Dusky Canada Geese. The 9.2 magnitude earthquake created drier conditions and promoted growth of vegetation which mammalian predators began to utilize as breeding grounds. The delta rose an average of 6.7 feet, allowing terrestrial as well as aerial predators access to Dusky nests.

 

Studies conducted by the Alaska Department of Fish and Game suggest that Bald Eagles are the most significant predator to the Dusky Canada Geese. Habitual patterns of Bald Eagles shifted after the earthquake and in turn impacted the Dusky population considerably. Wildlife biologists, David Crowley’s wildlife management report states that “the dusky population declined from 16,000 in 1990 to 6,700 in 2009.” The U.S. Forest Service has begun to survey these species to determine the breeding patterns and population trends of Dusky Canada Geese and the nesting habits of Bald Eagles.

 

The Dusky Canada Goose Subcommittee of the Pacific Flyway Study Committee proposed the Management Plan for the Dusky Canada Goose which aims to “provide guidance for the conservation of Dusky Canada Geese by implementing specific management actions and research needs to achieve a population of 20,000 breeding birds based on biological, economic, and social factors and historical population estimates.” Due to the increase of nest depredation (attacks on nests) over the last 70 years, the U.S. Forest Service has started to identify predators “causing significant gosling mortality and low productivity” as “the ultimate cause of population decline.”

 

To decrease gosling mortality rates, over 300 artificial nests have been spread throughout Cordova’s lakes, rivers, and ponds. These floating plant boxes are covered in vegetation and serve as a nesting island for mother geese during breeding season. The nests are located remote in areas far from Bald Eagle habitats, closer to the exterior of the Alaganik Slough.

 

Standifer and his coworkers take an airboat ride out to these locations weekly to determine the condition of the gosling eggs and retrieve photographs from motion activated cameras placed next to the nests. The team splits up, paddling in kayaks in deep water and wading and pulling the boats in the shallows to the nearest nest location.

 

The highest retesting rate of these nests has been six eggs, meaning that when these birds form a new nest, they typically lay up to six eggs. However, it is not guaranteed that all eggs will hatch. By evaluating the state of the shell and membrane of an empty egg, Standifer is able to determine whether or not the chick was eaten by a predator or hatched normally. Cameras which take photographs every 20 seconds are used to support the on-site data collected. Not only is one able to record when the hen leaves its nest, but also any predators who pay a visit.

 

The environmental changes in the Alaganik Slough allude to an ecosystem that had to adapt to a  changing climate. The ecological community which inhabits the Cordova region is continually adjusting to changes in temperature and landscape. The aerial prey and predators who contribute to the Alaganik Slough’s food web are continually altering their habitual patterns to align with the current climate.

 

 

Cristensen, Harriet H, et al. “Alaska's Copper River: Humankind in a Changing World.” United States Department of Agriculture Forest Service, July 2000.

 

David, Crowley W. “Management of Mammalian Predators of Dusky Canada Geese on the Copper River Delta, Alaska.” Alaska Department of Fish and Game Division of Wildlife Conservation, June 2011.

 

Shellhorn, Dick. “From Nothing, Cordova Moose Grew into a Healthy Population.” Anchorage Daily News, 2 Dec. 2017.

 

Dusky Canada Goose Subcommittee of the Pacific Flyway Study Committee. “Management Plan for the Dusky Canada Goose.”  Pacific Flyway Council U.S. Fish and Wildlife Service, revised July 2015.

 

“1964 M9.2 Great Alaskan Earthquake: Alaska Earthquake Center.” Alaska Earthquake Center. University of Alaska Fairbanks.

 

 

 

 

 

"To decrease gosling mortality rates, over 300 artificial nests have been spread throughout Cordova’s lakes, rivers, and ponds.'

About

Evan Standifer finds himself trudging through the Alaganik Slough just outside of Cordova, Alaska, on a weekly basis, conducting surveys of Dusky Canada Geese - a subspecies of geese that breed solely on the Copper River Delta in the summer and migrate south toward Fern Ridge Reservoir, just west of Eugene, Oregon, in the winter months.

 

The 1964 Great Alaska Earthquake, with its epicenter located 12 miles north Prince William Sound, largely affected such aerial species which prompted the current study of Dusky Canada Geese. The 9.2 magnitude earthquake created drier conditions and promoted growth of vegetation which mammalian predators began to utilize as breeding grounds. The delta rose an average of 6.7 feet, allowing terrestrial as well as aerial predators access to Dusky nests.

 

 

 

 

 

 

 

 

 

 

 

Studies conducted by the Alaska Department of Fish and Game suggest that Bald Eagles are the most significant predator to the Dusky Canada Geese. Habitual patterns of Bald Eagles shifted after the earthquake and in turn impacted the Dusky population considerably. Wildlife biologists, David Crowley’s wildlife management report states that “the dusky population declined from 16,000 in 1990 to 6,700 in 2009.” The U.S. Forest Service has begun to survey these species to determine the breeding patterns and population trends of Dusky Canada Geese and the nesting habits of Bald Eagles.

 

The Dusky Canada Goose Subcommittee of the Pacific Flyway Study Committee proposed the Management Plan for the Dusky Canada Goose which aims to “provide guidance for the conservation of Dusky Canada Geese by implementing specific management actions and research needs to achieve a population of 20,000 breeding birds based on biological, economic, and social factors and historical population estimates.” Due to the increase of nest depredation (attacks on nests) over the last 70 years, the U.S. Forest Service has started to identify predators “causing significant gosling mortality and low productivity” as “the ultimate cause of population decline.”

 

 

 

 

 

 

 

 

 

 

 

To decrease gosling mortality rates, over 300 artificial nests have been spread throughout Cordova’s lakes, rivers, and ponds. These floating plant boxes are covered in vegetation and serve as a nesting island for mother geese during breeding season. The nests are located remote in areas far from Bald Eagle habitats, closer to the exterior of the Alaganik Slough.

 

Standifer and his coworkers take an airboat ride out to these locations weekly to determine the condition of the gosling eggs and retrieve photographs from motion activated cameras placed next to the nests. The team splits up, paddling in kayaks in deep water and wading and pulling the boats in the shallows to the nearest nest location.

 

 

 

 

 

 

 

 

 

 

 

 

The highest retesting rate of these nests has been six eggs, meaning that when these birds form a new nest, they typically lay up to six eggs. However, it is not guaranteed that all eggs will hatch. By evaluating the state of the shell and membrane of an empty egg, Standifer is able to determine whether or not the chick was eaten by a predator or hatched normally. Cameras which take photographs every 20 seconds are used to support the on-site data collected. Not only is one able to record when the hen leaves its nest, but also any predators who pay a visit.

 

The environmental changes in the Alaganik Slough allude to an ecosystem that had to adapt to a  changing climate. The ecological community which inhabits the Cordova region is continually adjusting to changes in temperature and landscape. The aerial prey and predators who contribute to the Alaganik Slough’s food web are continually altering their habitual patterns to align with the current climate.

 

 

Cristensen, Harriet H, et al. “Alaska's Copper River: Humankind in a Changing World.” United States Department of Agriculture Forest Service, July 2000.

 

David, Crowley W. “Management of Mammalian Predators of Dusky Canada Geese on the Copper River Delta, Alaska.” Alaska Department of Fish and Game Division of Wildlife Conservation, June 2011.

 

Shellhorn, Dick. “From Nothing, Cordova Moose Grew into a Healthy Population.” Anchorage Daily News, 2 Dec. 2017.

 

Dusky Canada Goose Subcommittee of the Pacific Flyway Study Committee. “Management Plan for the Dusky Canada Goose.”  Pacific Flyway Council U.S. Fish and Wildlife Service, revised July 2015.

 

“1964 M9.2 Great Alaskan Earthquake: Alaska Earthquake Center.” Alaska Earthquake Center. University of Alaska Fairbanks.