Canadian Geese on the Local Diversity of Native Bird Species

If you are a resident of Tri-cities in Bay Area (Fremont, Newark Union City), California you will be well versed with the Canada Goose (or Canadian geese) population present within their parks and local communities, typically seen flying in a V formation in the sky and laying their waste upon urban structures and sidewalks.

Frequently traveling in groups, their presence has been carefully watched by birdwatchers and wildlife biologists, and are considered an “invasive” species across the country due to their major presence in the cities’ parks from their introduction many decades ago into the US(NYS Dept. of Environmental Conservation). The destructive nature of Canadian Geese however, are not limited to their intimidation and chasing of the residents at parks and wildlife reserves. The introduction and invasion of Canadian geese within Fremont is directly reducing the local biodiversity of native bird species.

Canadian geese are an invasive species thriving in Fremont due to unique factors within its suburban environment. Resident Canadian geese populations have increased rapidly in Fremont and similar urban areas since the 1950s, with one documented growth estimated to be an increase of 250% from 2007 to 2010 in Lake Merritt, located in Oakland. (Lake Merritt Canada Goose Management Study). Lake Merritt is similar to the conditions of manmade lakes in Fremont, which is also near Oakland, meaning the same growth would have been experienced in Fremont as well. In both cities, the sharp increase of Canadian geese is attributed to the lack of predators and environmental stressors, furthering breeding among the geese within the Bay Area. Within Fremont however, specific habitat factors can be linked to the overpopulation of geese. Parks and recreational lakes such as Lake Elizabeth provide free food from garbage cans and picnic events hosted on the shore, prompting the geese to stay at the parks (City of Fremont). With a supportive lifestyle, the need to migrate decreases, and geese as a result stay in these ecosystems. The rapid city expansion into the hills, based on the THINK Fremont development plan to support thousands of more residents, also eliminates direct predators of the geese, with resulting habitat fragmentation making it harder for coyotes from Coyote Hills and Mission Peak to reach residential geese populations (Carson). The lack of danger in the city increases their comfortability in the environment, allowing them to adapt even more quickly to higher altitude habitats near Mission Peak and Vargas Plateau, and venture out to less suitable ecosystems with more environmental disturbances.

The expansion of local Canadian geese is harming the local biodiversity of avian animals and reducing the population of large sized birds. Canadian geese can drop up to 1.5 pounds of feces every day, much larger than the typical weight of droppings laid by other native Fremont birds (Gordon). Therefore, the rapidly increasing population of Canadian geese is directly increasing the quantity of feces dropped by these birds every day. With Merritt’s lake resident geese population of 200-400 (Lake Merritt Canada Goose Management Study), there is an estimated total of around 300 to 600 pounds of droppings per day, not accounting for other residential geese populations. Due to the geographic location and habitat size, a similar dropping count can be reported in neighboring cities like Fremont as well. Due to Canadian geese being a versatile, generalist waterfowl species, they like to occupy several habitats close to large bodies of water across the Bay Area to be near freshwater and nutrient rich grassland. Areas like Tule Ponds, Elizabeth Park, Coyote Hills are frequent habitats of these geese, and as a result, they typically lay droppings in these local bodies of water, which are all interconnected through the Alameda Creek and other waterways. The hundreds of pounds of feces in the waterways poses a threat to local water ecosystems, as feces can contain several harmful bacteria like E.coli and salmonella and can cause harmful algae blooms, removing oxygen from marine systems. Due to this, fish populations of trout and other aquatic species will suffer.  Local native populations of pelicans, egrets, and herons, which are already low in count, will decrease, with their major sources of fish being contaminated or gone. The removal of a top predator within these ecosystems will trigger a trophic cascade, possibly endangering several more avian species who rely on the freshwater ecosystems. An adverse effect of accumulated geese feces causes insect populations such as mosquitos to rise inversely to the fish populations who feed on them. Without aquatic predators, these smaller insects will thrive, favoring populations of smaller native birds like the long-billed dowitcher and Wilson’s snipe who feed on them (Ebaxtor; Audubon). The shift in bird size and food sources will decrease the biodiversity of birds, with the environment selecting for those smaller in size and beaks specialized for insect picking, and eliminating larger native species of birds.

The rising population of Canadian geese due to an increased reliability on the Fremont habitat and increased tolerance of disturbed environments can affect the local diversity of native bird species, by selecting for smaller sized bird populations and eliminating the niche and need for larger birds of prey. With these changes, ecotourism and local bird watching programs will be harmed, decreasing historical wildlife recognition and economic revenue of wildlife conservation and organizations based within Fremont like Tule Ponds, Natural Children’s History Museum, and Masonic Homes. This economic damage will also effectively seep into Fremont’s city budget, which without funding, will cause further cuts for environmental opportunities for education. Furthermore, the toxification of water from geese droppings will harm profit and access of clean water sent through by the Alameda County Water District. Due to all these effects, action must be taken in order to either cut down or deter the local Canadian geese population in Fremont in order to preserve our native wildlife and water sources from further harm and provide a future in which birds, big and small, can live in our communities.

Note: 

This work was part of the essay that I did for my AP Environmental Science class at WHS, Fremont, CA.

Prompt: Evaluate the ecological effects of Canadian Geese within Fremont on the health of local wildlife

Works Cited

Carson, Daniel. “Fremont Maps 10-Year Economic Development Plan.” Messenger, The News-Messenger, 19 Oct. 2018, https://www.thenews-messenger.com/story/news/local/2018/10/19/fremont-maps-10-year-economic-development-plan/1687254002/. 

Ebaxter. “Long-Billed Dowitcher.” Ask A Biologist, 13 July 2017, https://askabiologist.asu.edu/activities/bird/long-billed-dowitcher. 

Lake Merritt Canada Goose Management Study, Jones and Stokes, Oakland, CA, 2007. 

Ligon, Published by Gordon. “Goodbye Geese.” Goodbye Geese, 15 Dec. 2017, http://goodbyegeese.net/2017/12/15/the-hidden-dangers-of-goose-droppings/#:~:text=Canada%20Geese%2C%20on%20average%2C%20drop%20between%201%20to,a%20real%20threat%20to%20humans%20and%20pets%20alike. 

“Nuisance Canada Geese.” Nuisance Canada Geese - NYS Dept. of Environmental Conservation, https://www.dec.ny.gov/animals/7003.html. 

“Picnic Area Reservations: City of Fremont Official Website.” Picnic Area Reservations | City of Fremont Official Website, https://fremont.gov/331/Picnic-Area-Reservations. 

“Wilson's Snipe.” Audubon, 20 Oct. 2021, https://www.audubon.org/field-guide/bird/wilsons-snipe.