Ah spring, a beautiful time of year. Warm, sunny, and all the birds come back from their winter getaways to hurry towards the cooler north. What’s that all about anyways – why do they leave in the first place?
Birds migrate in order to find more resources – either food or nesting locations. Migration is the seasonal movement of animals from one area to another, but it doesn’t just happen north-south, and it’s not just birds who migrate either - Caribou, Salmon, and even butterflies undertake migrations as well!
Most of our songbirds in Canada rely, at least in part, on insects to live. While insect larvae must survive the winter too, most insects are asleep or developing as eggs in the winter, and are not very accessible to a lot of our songbirds. This, combined with cold temperatures, mean that many North American bird species migrate south for the winter, and only a few tough species stick around to endure the cold. Some species, such as the Snowy Owl, actually migrate to the Edmonton region in winter from their Arctic breeding grounds! Several other species migrate to the Edmonton in winter instead of summer as well, including Great Gray and Northern Hawk Owls, as well as Snow Buntings and Redpolls.
Well, why do birds even bother to fly back to Canada in the spring then? The answer has to do once again with food. There aren’t many insects in winter, but there sure are a lot in summer. There are lots of birds competing for food on the wintering grounds, so many of our songbirds benefit from making the often 1000 km journeys up north to raise their young when food is plentiful. Greater day length in northern regions in the summer might also be a reason why some birds migrate long distances, allowing them to raise more young.
There are a lot of factors to consider in such a long distance migration – birds who get there first might get the best territories and find a good mate. But birds who fly too early could risk starvation if food Is not available yet.
Human influences can sometimes allow species to overwinter where they would not historically have done so. Two good examples are American Robins and Mallard Ducks. There are so many heated buildings in cities that the average outside temperature within a city is warmer than outside of the city, allowing Robins to sometimes live out the winter in Edmonton and area. Another example is Mallards – they require open water to overwinter, which is not available in this area – except where warm water enters the river from waste treatment plants. There are definitely some benefits to sticking around, but some pretty high risks too.
They are beginning their journeys north to breed, and we are waiting with anticipation!
So watch closely this spring for your favorite bird to appear, and you can even watch bird migration forecasts online, then make a record of your sightings on ebird to contribute to Citizen Science!
Cornell Lab of Ornithology. (2007). The Basics Of Bird Migration: How, Why, And Where. Retrieved from https://www.allaboutbirds.org/the-basics-how-why-and-where-of-bird-migration/#