It is later in March and it is currently snowing. Sure, we get late snowstorms, but there’s still several feet of snow, the river is still frozen, and the daily temperatures still sit below freezing regularly. This is definitely a late spring. But the Canada geese are back from their yearly migration, searching for food where the snowpack is slowly dwindling thanks to a slightly more powerful sun at present. But this got me wondering, what triggers a goose to nest? Different animals and plants respond to different triggers including day length, temperatures, and food availability. So what makes a goose decide that now is the time to lay eggs?
Clermont, Reale, and Giroux (2018) investigated this very question. Phenology is the fancy word for the study of seasonal changes. The podcast Ologies has an entire episode on the topic if you’re interested. And it’s a pretty big topic at the moment as the timing of seasons changes with climate change. The ability of a species to change parts of their phenology like when to reproduce could make the difference for whether they survive or not. If you always reproduce at the same time you risk it being too cold, or too hot, or there might not be enough food.
Canada geese, it turns out are pretty flexible in terms of when they lay eggs. In biology, the ability to change based on conditions is called plasticity and geese have high plasticity when it comes to laying dates. So what signal are the geese waiting for? The maximum temperature. Up here, where I live in Canada at least, this probably bodes well for the geese. While they are dealing with high levels of snow coverage and most likely limited food availability, they at least aren’t also adding young mouths to feed as well.
This plasticity will likely also benefit the geese in the face of climate change. We know that global temperatures are increasing with climate change, but that is an average across the board. This change in temperature has the ability to impact seasons, extreme weather, and daily temperatures in many ways. Every day will not be warmer, there will be more variation and more extreme events. As a result, animals that are more flexible in their life history, doing things like eating different types of food, or, like the geese, adjusting when they lay eggs based on immediate conditions, will have an advantage and are more likely to survive as we change the world even more than we already have.