Course:CONS200/2021/A conservation success story? The recovery of the Canada Geese in North America and remaining challenges.

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A Canada Goose swimming.
A Canada Goose swimming in Palatine, Illinois, USA.

The Canada Goose (Branta canadensis) is a species of goose native to both arctic and temperate regions of North America.[1] Introduced populations are also present in a few western European countries.[2] Often found in cities, they are able to adapt to the presence of humans well.[3] They feature an easily recognizable pattern, with a brown body and mostly black head and neck, with white patches extending from the throat to the eye. They are long-lived birds with relatively high survival rates and low reproductive rates, exhibiting very strong bonds between families and breeding pairs and often returning to their natal homes to nest.[4] Generations of geese often last around 10.5 years.[2] The Canada Goose is primarily a herbivorous bird, preferring a diet of mainly grasses, aquatic plants, sedges, berries, grains, algae, and seeds.[3] 7 subspecies are currently recognized; the Atlantic, Hudson Bay or Interior, Giant, Moffitt's or Great Basin, Lesser, Dusky, and Vancouver. The different subspecies tend to be smaller moving northward, and the colouring of their plumage tends to become darker moving westward.[5] The overall distribution and population size of Canada Geese is decided by many biotic and abiotic factors.

Population Decline

Four Canada Geese flying to a farmers field.
Four Canada Geese flying to a farmer's field near Chilliwack, BC, Canada.

Canada Geese faced a dramatic decline in their population in the early 1900s as a result of unregulated hunting, egg collecting and habitat destruction. Soon after, in 1918, The Migratory Bird Treaty Act was passed, which established regular hunting seasons in an attempt to mitigate this population loss and protect wild birds. However, by 1962 the drainage of wetlands in the Eastern United States began to exacerbate the issue.[4] Along with this, U.S. hunters were still harvesting an average of 1 million geese per year throughout the 1960s.[6] The combination of all of these factors brought the Canada Goose population to near-extinction levels. They were believed extinct for almost 30 years, until a very small population was discovered by Harold C. Hanson, in the early 1960s nearby Rochester, Minnesota. Isolated populations of Canada Geese, including those kept in captivity by aviculturists, were found and believed to be a promising option to begin restoring the species’ population.[4] These birds were larger than other Canada Geese and didn't migrate in fall, which gave rise to the common misconception that they had domestic origins.

Migratory Birds Convention Act

An international treaty between Canada and the United States called the Migratory Birds Convention was signed in 1918, when the Canada Goose was on the brink of extinction.[7] In 1994, after the population's numbers had been stabilized, a legal act was created on the basis of this treaty; the Migratory Birds Convention Act, (MBCA).[7] Canada Geese are included in this act, which provides protection and aids conservation efforts for migratory birds. Furthermore, it prohibits people from harming these birds outside of very specific conditions. However, several species of these migratory birds, including Canada Geese, are considered game birds and may still be hunted. This act gives the federal government the responsibility to establish hunting seasons, and ensure the species is not hunted to an excessive or harmful degree in the future.[7]

A Canada Goose in its nest, with young goslings peeking out.
A Canada Goose in its nest, with young goslings peeking out.

Early Habitation

Though there is not much relevant data present from before the 1960s, according to early conservationists Canada Geese historically nested in much of southern Canada. The grasslands and wetlands of southwestern Ontario and the southern prairies supported breeding populations of Canada Geese at the time of settlement, although it is unknown how many birds were present at these times.[5] In the modern day there are more suitable habitats available for geese as a result of human activities, so it is likely that there were markedly fewer Canada Geese in the early-mid 1960s than there are today.[5] These changes to the landscape also benefit the Canada Geese nesting in subarctic regions. Due to global warming and industrialization, some areas that were once uninhabitable are now desirable habitats for the species. In other parts of North America, Canada Geese are not a native species and are present as a result of intentional introduction by humans. Both introduced (southern British Columbia, Québec, and Maritime provinces) and indigenous (southern prairie provinces and southern Ontario) populations have grown at an extraordinary rate in recent years.[5]

Rediscovery by Harold C. Hanson

Harold C. Hanson (1917-2003) was born in Chicago, Illinois. He graduated with a Bachelors of Arts in Biology, and then received his Master of Science degree in Wildlife Management in 1943 from the University of Wisconsin. By 1958, Hanson had received his PhD in Ecology and Physiology from the University of Illinois.[8] His major research focused on wild geese, specifically the Canada Goose. He was a part of numerous field studies and expeditions to Greenland, the central Canadian Arctic, the Hudson's Bay region, and Mexico.[8] He worked as an adjunct Professor of Zoology at the University of Illinois for much of his life, and was also a wildlife specialist for the Illinois Natural History Survey for many years.[8] Dr. Hanson’s most noteworthy contribution to science was the rediscovery of the giant Canada Goose (Branta canadensis maxima), documented by his book "The Giant Canada Goose" (1965)[8]. During the last years of his life he worked on a multi-volume treatise titled "The White-cheeked Geese" (2006); this work examined the identification of various subspecies of Canada Geese, and correlated geology and climate with their evolution.[8]

Population Growth

A group of Canada Geese swimming.
A group of Canada Geese swimming.

Despite the near extinction of Canada Geese in the mid 20th century, populations have greatly recovered over the last 50 years. Canada Geese are continuing to see an increasing population trend.[2] Within the last few decades, non-migratory populations of Canada Geese (Branta canadensis) are now established within metropolitan areas across North America. These non-migratory populations in North America have been so successful that their numbers have amplified 16-fold over the last three decades, and reached a total population of 5.5 million during 2008.[9] They now outnumber migratory Canada Geese in all North American flyways.[10] Substantial research of Canada Geese observed in New Haven County and Connecticut by Michael R. Conover shows that populations have increased steadily since the 1950s, when less than 500 geese were observed annually. numbers greater than 16,000 were observed by the start of Conover’s study (1984) and had grown to over 52,000 by the end of Conover’s study (2009).[10] Many factors have had a great influence on the increasing populations of Canada Geese.

Contributing Factors

A contributing factor to the tremendous resurgence of Canada Geese is the areas these new populations inhabit. It has been found that a great number of Canada Geese started nesting in New Haven County and Connecticut during the 1970s.[11] The terrain in these areas is mostly flat near the coast of Long Island Sound, which is on the state's southern border, and rises to low hills (up to 320 m) in the northern part of New Haven County.[12] A majority of Canada Geese in New Haven County built their nests on abandoned Muskrat (Ondatra zibethica) lodges and Mute Swan (Cygnus olor) nests that were scattered on islands, ponds and lakes throughout the county.[12] The Canada Geese were non-migratory and rarely left the county once they began nesting there.[10] Parents brought broods to 1 of 3 brood-rearing sites there, sometimes travelling several kilometres to reach them.[12] The county contains abundant ponds, streams, and rivers; several reservoirs have been created there to provide power or store water.[12] The presence of these ponds and lakes has positively influenced Canada Goose populations since they provided a constant water supply for the birds. Additionally, many goose parents in New Haven County have moved their broods to golf courses or other sites where there were mowed lawns that offered abundant food for their goslings.[10] The golf courses and other sites offer the geese populations established food security, thus contributing to their recovery rates. The abandoned nesting areas, water availability, and abundance of food assisted the immense resurgence of Canada Goose populations.


A leg band, used to study the movement and distribution of wild birds.

Banding wild birds is a strategy in which auxiliary markers and leg bands are attached to waterfowl in order to study their movement and distribution, as well as to estimate survival levels and population sizes.[6] Canada Geese banded in Iowa (145,743 km2) were recovered throughout the central part of North America in the United States and Canada between 1999 and 2019.[13] These geese banded in urban areas had a higher survival rate, and lower dead recovery rate than geese banded at rural sites. Survival continued to increase for urban-banded juveniles, and recovery rates were also seen to increase during the liberalization of harvest regulations. They were then seen to decrease again once regulations had stabilized. These results suggest that Canada Geese bred in urban areas contribute to harvest, and specialized regulations can affect these populations.[13]

Hunting Restrictions

Great efforts have been made for the restoration of Canada Geese through several established closed areas to goose hunting, restricted harvest regulations, and the translocation of populations. Canada Goose harvest regulations were opened in areas containing only 32% human population conductive to increase harvest and reduce conflict.[13] Urban goose management zone regulations mainly consist of a special urban season in early-to-mid-September with a daily limit of 5 Canada Geese. Consequently, the focus on restoration, management of harvest, and solving human-goose conflict could lead to further increases in the Canada Goose population.[13]

Current Distribution

IUCN Red List Category

Canada Geese are considered to be of Least Concern (LC), the least endangered of any category on the Red List, as of 2018 when they were most recently globally assessed by the IUCN.[2] This has been their classification since they began being evaluated in 2006.[14] Due to their extremely large range of 23,300,000 km2, the Canada Goose does not approach the thresholds for Vulnerable classification under the range size criterion (extent of occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation).[14] Along with this, their population trend appears to be increasing, so they does not approach the thresholds for Vulnerable classification under the population trend criterion (>30% decline over ten years or three generations) either.[14] Finally, their current population size is extremely large, and does not approach the thresholds for Vulnerable classification under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure).[14] As a result, Canada Geese have been evaluated as a species of Least Concern.

Global distribution of Canada Geese as of 2006.


The map to the right is a visual representation of global Canada Goose distribution as of 2006, created by Andreas Trepte (CC BY-SA 3.0):

  • Dark yellow: native summer breeding populations.
  • Light yellow: introduced summer breeding populations.
  • Dark green: native year-round populations.
  • Light green: introduced year-round populations.
  • Dark blue: native winter populations.
  • Light blue: introduced winter populations.
  • Pink: breeding range of the Cackling Goose (Branta hutchinsii), closely related to the Canada Goose.

Current Conservation Actions

Many conservation actions are still in place for Canada Geese today. These include but are not limited to systematic monitoring schemes, identified conservation cites, protected areas, inclusion in international legislation, and international management and trade controls.[2]

Remaining Challenges

A Canada Goose and goslings on the beach.
A Canada Goose and goslings on the beach at Cultus Lake, BC, Canada.

Canada Geese have been brought back from the edge of extinction, and removed from the endangered species list. In fact, their recovery has been so rapid in some areas of Canada and the United States that they have become overabundant, posing serious concerns for farmers and homeowners.[15] David Drake, a professor of forest and animal ecology at the University of Wisconsin-Madison and a UW-Extension wildlife specialist, recognizes concern about techniques which have been used to manage Canada Goose populations but believes they are important.[16] According to Drake, the overabundance of geese brought with it a slew of other environmental and safety concerns. Geese can be violent, resulting in human injury if they attack.[16] Some local governments facing problems due to the overabundance of Canada Geese are able to request permission to destroy nests and eggs in order to mitigate population growth.[2]

Effects on our Ecosystem

Bread, crackers, and other high-carbohydrate products are junk food for Canada Geese. They are low in nutritional value, and birds who eat them will not seek out other more nutritious foods as a result. This can lead to malnutrition in the geese, which can lead to a variety of health issues in their offspring.[17] Thus, artificially fed geese often develop wing deformities such as "angel wings". This occurs when their joints are unable to fully form while the wing and feathers develop, and the weight of the increasing feathers spins the tip of the bird's wing.[18] It is also possible for feeding geese to pollute the local ecosystem. Bread that goes uneaten can decompose and emit foul odours as well as encourage the growth of algae, which then goes on to clog rivers, putting fish and other creatures at risk.[17] Canada Geese are also prone to overgrazing, which can lead to the erosion of water banks, and hold the potential to pollute fields and rivers with their feces.[16]

Effects on the Public

Canada Geese can be extremely hostile and possessive, especially from March through June due to their breeding season. They will begin to molt all of their flight feathers leaving them unable fly, and are usually very defensive of their nests or goslings during this time.[19] If people continue feeding a population of geese they will become comfortable with the human presence, and will begin building their nests closer to busy urban areas.[16] Canada Geese can become conditioned to and reliant on receiving food from humans early in their life. They will become increasingly aggressive and lose their fear of humans over time as a result. Some geese will suffer because they are unable to compete for food.[19]

Climate Change

Climate change and the severe weather that comes with it could potentially threaten Canada Goose population sizes. Considering current projections, it is likely that they will be forced to shift their habitat due to these factors.[2] These changes are expected to affect more than 90% of the Canada Goose's habitat in the future.[14]


Canada Geese have faced many threats to their population, including a period of near extinction in the mid-20th century, but the species has miraculously recovered. They experienced a sharp decline in their populations due to unregulated hunting, egg collecting and habitat destruction in the early 1900’s, with the greatest threat to the Canada Geese being were hunters who were harvesting a disproportionate number of geese.[20] In the 30 years following this, Canada Geese were thought to be extinct. Fortunately, due to immense research done by Harold C. Hanson, a remnant of the population was discovered and then utilized in efforts to repopulate the species.[4] Canada Geese were also then protected by the establishment of the Migratory Birds Convention Act in 1994. Additionally, the introduction of Canada geese to areas with abandoned nests, water availability, and an abundance of food greatly assisted the recovery of the Canada Goose population.[10] Various efforts have been made for the restoration of Canada geese since then, including established areas closed to goose hunting, strict harvest regulations, and the translocation of populations to new, more suitable habitats.[13] Thus, the populations of Canada Geese throughout North America have been effectively restored and stabilized.[13] All of this combined is widely seen as a success story in terms of conservation.

Despite the recognized success of conservation in terms of Canada Geese, there have also been downsides as a result of their increasing populations. The species has since become substantially overpopulated, presently being categorized as Least Endangered on the Red List assessed by the IUCN.[2] Population numbers have continued to increase exponentially, with the species now being seen as a nuisance and being known to cause significant problems for the public in the urban areas they inhabit.[16] The overabundance of Canada Geese throughout the continent has lead to both environmental and public safety concerns.[16] The remaining challenges caused by their overabundance are now placed onto local governments, who must find sustainable ways to contain the species, while also being careful not to drive them to near-extinction once again.[2]


  1. "Branta canadensis". Integrated Taxonomic Information System. Retrieved 6 December 2021.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 BirdLife International (9 August 2018). Branta canadensis. The IUCN Red List of Threatened Species. Retrieved 7 November 2021.
  3. 3.0 3.1 Pierce, J. R. (August 2016). "Understanding and Managing Resident Canada Geese in Vancouver" (PDF). Retrieved 6 December 2021.
  4. 4.0 4.1 4.2 4.3 Graber, D. A.; Coluccy, J. M. "Understanding Waterfowl: Story of the Giants". Ducks Unlimited. Retrieved 7 November 2021.
  5. 5.0 5.1 5.2 5.3 "Canada Goose". All About Birds. Retrieved 7 November 2021.
  6. 6.0 6.1 Coluccy, J. M. "Understanding Waterfowl: Waterfowl Bands and Other Markers". Ducks Unlimited. Retrieved 7 November 2021.
  7. 7.0 7.1 7.2 "Migratory Birds Convention Act, 1994". Justice Laws Website. Archived from the original on 1 January 2003 |archive-url= requires |url= (help). Check date values in: |access-date= (help); Missing or empty |url= (help); |access-date= requires |url= (help)
  8. 8.0 8.1 8.2 8.3 8.4 "Information on Harold C. Hanson" (PDF). Luther College. Retrieved 9 December 2021.
  9. Dolbeer, R. A., & Seubert, J. L. (August 2009). "Canada goose populations and strikes with civil aircraft, 1990–2008: challenging trends for aviation industry". University of Nebraska-Lincoln. Retrieved 7 December 2021.CS1 maint: multiple names: authors list (link)
  10. 10.0 10.1 10.2 10.3 10.4 Conover, M. R. (1 December 2011). "Population Growth and Movements of Canada Geese in New Haven County, Connecticut, During a 25-year Period". BioOne. Retrieved 7 December 2021.
  11. Conover, M. R.; Chasko, G. G. (1985). "Nuisance Canada Goose Problems in the Eastern United States". 3. 13: 228–233 – via JSTOR.
  12. 12.0 12.1 12.2 12.3 Conover, M. R., & Frank, M. G. (2018). "Determinants of growth rates and mass of canada geese goslings". The Journal of Wildlife Management.CS1 maint: multiple names: authors list (link)
  13. 13.0 13.1 13.2 13.3 13.4 13.5 Luukkonen, B. Z.; Jones, O. E., III; Klaver, Robert W. (21 December 2020). "Canada Goose Survival and Recovery Rates in Urban and Rural Areas of Iowa, USA". The Journal of Wildlife Management. 85 (2).
  14. 14.0 14.1 14.2 14.3 14.4 "Canada Goose Branta canadensis". BirdLife International. 2021. Retrieved 9 December 2021.
  15. Berget, J. (16 March 2021). "Why it's illegal to kill Canada Geese even though everyone has considered it". The Other Press. Retrieved 7 November 2021.
  16. 16.0 16.1 16.2 16.3 16.4 16.5 McCoy, M. K. (16 July 2018). "Wildlife Expert: Canadian Geese Culling A Necessary Practice". Wisconsin Public Radio. Retrieved 7 November 2021.
  17. 17.0 17.1 Schweig, S. V. (3 April 2017). "Here's Why Feeding Geese And Ducks Is Bad For Them". The Dodo. Retrieved 3 December 2021.
  18. "What is Angel Wing Syndrome". Chicago Academy of Sciences Nature Museum. 12 May 2016. Retrieved 3 December 2021.
  19. 19.0 19.1 "Canada geese are in nesting season, causing aggressive behavior". Your News Now. 17 April 2019. Retrieved 5 December 2021.
  20. Petrie, M. "Geese in the 21st Century". Ducks Unlimited. Retrieved 7 November 2021.
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This conservation resource was created by Macy Pamplin, Rachael Kim, Casandra Lee, & Gracy Kapoor. It is shared under a CC-BY 4.0 International License.