Time To Fly South – The Wondrous World Of Bird Migration
This blog is written by Nature Canada member Steve Gahbauer and edited by Sam Nurse.
The summer peak is now long behind us. The sunlight is a little weaker, the flowers are drooping, the leaves of deciduous trees turn a brilliant colour and darkness creeps a little closer with each passing day. Nature is winding down and fall is here.
On crisp fall nights, shoals of Three-spine Sticklebacks sparkle in the moonlight, and Hooded Mergansers will make their annual visit. Noisy Greater Yellowlegs, returning from northern breeding grounds in August, linger until late November. A bit earlier, Ring-billed Gulls, that nest west of the Great Lakes, are winding up their migration to California and Mexico. By late November, Striped Skunks are looking for deep dens to spend the winter. By mid-December the breeding season is over for White-tailed Deer and female Red Foxes look for suitable dens.
This is also the time of big bird migration, one of the most extraordinary events in the natural world. It begins at the end of August and ends in late fall. Raptor migration peaks in September and October *. Every year, thousands of birds migrate along the main flyways. The scale of the avian movement is truly awesome. Billions of birds navigate mountains, oceans, deserts and adverse weather systems on their remarkable journeys.
Arctic Terns fly some 17,700 kilometres in their circumpolar migration throughout their lifetime between their winter abode in Antarctica and their breeding grounds in northern Canada and Greenland. Non-stop distance flown by Hudsonian Godwits are up to 12,800 km. Semi-palmated Sandpipers fly 96 hours non-stop from the Bay of Fundy to South America. Whimbrels are among nature’s most impressive wayfarers. They breed in the northern wetlands and tundra around James Bay and Hudson Bay and winter more than half a world away in Brazil. A few years ago, one banded Whimbrel was tracked covering 5,057 km in 143 hours at an average flight speed of more than 35 km/h!
Of the birds that breed in Canada, 90% migrate. Shorebirds, like the ones mentioned above, are the most accomplished travellers. For most migrating birds, the journey takes three to four weeks. What helps them to make those long and arduous migrant flights is the way they breathe. Another thing that makes migration flights possible is the great versatility of a bird’s wings. To conserve energy, birds have to do their wing-beating in flight as economically as possible. One simple method of achieving that is to stop beating wings every now and then or regularly interrupt rapid wing beats. Bigger and heavier birds have developed other ways to economize on their wing beats like gliding in flight. Raptors and pelicans are known to do this regularly.
With these long migrations, birds are likely to encounter challenges along the way. One challenge for birds is climate change as it can effect them in various ways. It alters their distribution, abundance, behaviour, and even their genetic make-up. Migration and breeding times are changing, the availability of food and nesting material changes, and there may be new parasites and predators to which they are not adapted. Other concerns are degradation and loss of critical stopover sites, such as coastal wetlands. A number of migrating species are already responding to climate change by northward adjustment in their distribution, upwards shift in altitudinal ranges, and earlier breeding seasons.
There needs to be a stronger focus on conservation and education. We know so little about our feathered friends, but the mystery of bird migration is slowly being unlocked. With modern technology now allowing us to track even small migratory birds, the opportunities for new discoveries are endless. It is now possible to track birds by satellite, which has revolutionized our understanding of their migration routes and wintering grounds.
* Toronto’s High Park hawk watch ranks with Beijing and Istanbul as one of the world’s three best spots for observing migratory raptors in an urban setting. Other good hawk-watching places include Cranberry Marsh in Whitby, Hawk Cliff and Holiday Beach on Lake Erie near London and Windsor, respectively, the Leslie Spit in Toronto, and East Point Park in Scarborough.
Sources: Canadian Wildlife Federation, Canadian Parks and Wilderness Society, Parks Canada, Bird Studies Canada, Birdlife International, Ontario Nature, Wild City (Bennet & Tiner), Microsoft eNews, Metro, and field notes.
For earlier Nature Notes essays visit www.rougevalleynaturalists.com and click on “Nature Notes.”