The Canada Goose (Branta canadensis) is a distinctive looking giant brown bird with a black neck and a white chinstrap marking. They are found everywhere in North America, all the way from Alaska down to the northern tip of Mexico and across the continent from coast to coast.
They’re familiar to almost everyone, and I was curious about their migratory patterns. They typically live upwards of 20 years and pairs will mate for life, but only until death do them part. They prefer marshes and grass and do not shy away from urban areas, especially where lawns are found. They forage on the ground to eat grasses, sedges, seeds, grains, and berries. They are considered pests in some areas but are also a protected species.
Data
There are at least 11 subspecies of Canada geese, some are resident (nesting within the lower 48 states) and some are migratory. For these visualizations I found data for two migratory subspecies (Branta canadensis interior and Branta canadensis maxima) in the North-East on www.movebank.org, a database for animal tracking data.
In a study spanning 2015-2021, Canadian researchers tracked the movements of 82 adult Canada geese tracked with GPS-tagged collars. Six of them were female and the rest were male. The size of the area studied is approximately 150,000 square kilometers, and the study included recommendations for indigenous hunters in the James Bay area to safely take advantage of harvesting opportunities during molting season.
To prepare the data for joining in Tableau I needed to concatenate some of the ID fields which were separated in some files and concatenated in others. At the end, to more easily filter and identify specific geese I asked ChatGPT to generate 82 names beginning with the letter G (6 female and 76 male).
At first, I created four maps for each of the seasons (winter, spring, summer, and fall, each covering three consecutive months of the year). However, upon closer inspection I noticed that there were distinct monthly variations that didn’t line up with the traditional meteorological seasons so I redefined the classification bins:
- November to February
- March to April
- May to June
- July to August
- September to October
Canada geese undergo an annual molt in the summer where they shed and re-grow their outer wing feathers. They’re flightless during this time (bin 4) and stay put for about 4-5 weeks, hanging out and enjoying safe spaces together until it’s time to move south towards milder weather again.
Maps
I mapped the point data for all 7 years (filtered by month according to the five bins listed above), encoded each goose with a colour, and added some attributes: sex, unique ID, and generated goose name. It’s interesting to see where they stop to molt and also how long some of the migration distances are.
Further analysis
These maps visualize all the years of the study together, from 2015-2021. Initially, I was curious if the Canada Goose migration patterns changed during the pandemic, but I’m not sure if this data is granular enough to show those patterns. Additionally, Canada Geese are typically pretty bold and not afraid of getting comfortable in extremely urban areas. While other animals may have mustered up the courage to spread out during the pandemic as humans locked down, Canada Geese may not have needed that courage.
I wasn’t able to add the timestamp to each point, perhaps there is a different attribute that needed to be added as a dimension to make that happen. Adding time data might mean I can add directional symbology so we can see which way the geese are migrating in each map. We can probably guess, but there are a couple of geese who veer from the group. For example, I’m not sure if Gabriella (light blue points during molting season) arrived in the north late or is flying south early.
I’ve also been unable to successfully upload the project to Tableau Public. It might be that there are too many points (over a million), but I’m not sure. It freezes my browser every time. The interactive version is a bit more interesting since it allows for selecting a goose by name to see their paths, so I hope to solve this problem sometime.
Sources
New York State Department of Environmental Conservation: Canada Goose