For many Canadians, the early morning sound of songbirds is one of the surest signs that spring has arrived. If from year to year the change of seasons falls a few days early or late, the change may go almost unnoticed by locals, but it can have a devastating impact on migratory songbirds.
Imagine that you are about to go on a trip, and while you know the route, you have no indication of the weather conditions at your destination, or even along the way. This is an unknown that these birds face. They also rely heavily on early-spring insects as a food source, and these come with the greening of the trees.
To make a best guess, birds look to the sun. As it begins to rise earlier, bringing longer days, they begin to migrate north.
But if they are too late, this can change the entire ecological community for these birds. They may miss out on hunting for enough early-spring insects to fuel their flight or to feed their young. They could also miss a critical window for finding prime locations to build their nests, which could be taken by local wildlife, or other migratory birds who were better able to adapt. This exposes them to predators and parasites.
And if they are too early, early-spring insects may not be available either, and they also risk facing freezing conditions with their new hatchlings.
Researchers from Memorial University of Newfoundland and Florida’s Museum of Natural History are looking to satellite data and observations from citizen scientists to track when migratory birds arrive in Canada. And what they found is that there is an ever-widening gap between the greening of biological spring and the arrival of many species of songbirds. For some species, that gap can be as wide as 15 days.
Climate change is continuing to trigger changes in the start of biological spring, with earlier greening in Eastern Canada, and later greening in Western Canada.
These changes could drive hundreds of bird species to extinction. Reduced biodiversity has already been recorded, and this is projected to continue.
With their new data in hand, researchers are looking to understand why some species are better able to adapt, and why others are falling behind.
While any policy changes may be too little too late for some bird species, this adds to the chorus of calls for change.