By Andrea McDowell, originally published September 22, 2010
Global warming and its effect on Toronto’s birds
Climate change often sounds like it’s something that happens somewhere else: the ice at the poles melts, island nations (and Manhattan) go under water, more Category 5 hurricanes in the Gulf of Mexico. But what about Toronto? OK, summer’s hotter, winter’s warmer, especially at night–does that sound so bad? (Though keep in mind that more heat means more smog, and smog kills about 1,700 people each year in Toronto.) A longer growing season? More shorts weather? We’re going to complain?
Well, yes. For one thing, those catastrophic weather events will hit here too. But forget about that. Humans are actually not the only living things in the city. Let’s take one example: birds.
Bird species that over-winter, such as chickadees, may increase. Winter will not be as deadly; food will arrive earlier in the spring. But migratory songbirds (whose populations have already declined by over 50% over the last four decades as a result of habitat fragmentation, pesticides, lighted office towers and tropical/boreal deforestation) will not fare so well. Their migration is frequently driven by hours of sunlight but the appearance of their food sources (plants, insects, etc.) is often driven by temperature. As climate change progresses and spring arrives earlier, the overlap of the migration routes and food sources will shrink, meaning that by the time the migratory songbirds get to Toronto their favourite tasty caterpillars will already have metamorphosed into butterflies and flown away.
This effect is more pronounced among bird species that migrate over longer distances. Experts hypothesize that it’s easier for birds to respond to changing climates by changing the timing of migration when the distance is short–say, the mid-US to southern Canada–because the climates are not as different, and the mid-US winter will offer clues about the onset of spring in southern Canada. But birds that winter in the tropics and fly each spring to Canada’s northern boreal forests have no such clues, and their migration timing is not shifting in response to the changing climate. Sadly, those are the very species whose populations are most suffering already from the issues listed above. For all these reasons combined, experts estimate that 30% of migratory songbirds may go extinct with a change in temperature of 2.0 degrees Celsius (which we have now already committed to, thanks to carbon already released to the atmosphere).
Hooded Warblers and Acadian Flycatchers are two songbird species that migrate to southern Ontario each year from the neotropics. Thanks to the disappearance of their preferred Carolinian forest summer habitat locally, Acadian Flycatchers are listed as endangered and Hooded Warblers as threatened; both species are already shifting their habitat northward in response to warming, though how far north they can go when Carolinian forests only exist in southern Ontario is anyone’s guess. The American Bird Conservancy projects that a doubling of CO2 levels will see American Goldfinches move north of Toronto; we are already nearly there.
So say goodbye to goldfinches, Hooded Warblers and Acadian Flycatchers; but you might be able to say hello to the Bobolink, a migratory songbird that currently lives only south of the Great Lakes but, due to warming, will soon be found, experts predict, only in Canada.
Spring may not be silent in a few decades, but it sure won’t sound the same.
Andrea McDowell coordinates environmental approvals and studies for wind energy projects by day and writes about environmental issues by night. This leaves twilight for hiking all over Southern Ontario’s conservation areas, parks and trails, taking photographs and cataloguing whatever she finds there at her blog Zoopolis (http://blog1.andreamcdowell.com). She has contributed to This Magazine, Spacing, Corporate Knights, Brain, Child and Rabble.ca. Send your questions or comments about natural heritage for possible use here to: email@example.com.
There are lots of things you can do to help out migratory songbirds in your community, no matter how urban it is, including:
1. use native plants in your yard and garden to give local wildlife a place to live
2. fight for conservation of local natural areas (birds can use these small areas as stopping grounds on their migration, giving them a chance to rest and eat before flying on northward)
3. build backyard and park habitat like nesting boxes
4. don’t use pesticides or herbicides; these little birds are extra vulnerable
5. volunteer for initiatives such as the annual Rouge Park bird count to give scientists the information they need to measure population and distribution trends
Climate Change and Birds (Nature Canada)