We have entered a thrilling time for raptors and now is the time to get out to a hawk count or a site along lake Ontario or Lake Erie to witness the event. As I am now living in Toronto, a few wonderful sites from the Essex County area are off limits to me for now including Holiday Beach Conservation Area (the 2007 Festival of Hawks is currently on there), Sea Cliff Park, Leamington, and Point Pelee National Park (hawks tend to filter into the peninsula and can often be seen migrating off the tip, only to return as there are no warm thermals over the lake). Another hotspot is Hawk Cliff, Port Stanley, which is located northeast of Rondeau Provincial Park.
Raptors need warm thermals to migrate, which are large ascending masses of warm air that form after being heated by the sun. These columns of warm air lift particles and water vapour and often form cumulus clouds (beneficial for hawk migration as finding a hawk on a white backdrop is much easier than finding them in a clear blue sky). This form of migration is evident when you see raptors 'kettling'; a group of hawks spiraling and rising in the air. Since warm air will not form over the cooler surfaces of lakes and bodies of water, raptors have to find land-routes during migration so the northern shores of the Great Lakes are great spots for witnessing raptor migration. Winds are also important. Intuitively, northern winds give that extra push that hawks need so that they expend as little energy as possible during migration (it's a long way for some, all the way to the tropics in fact).
Yet another current besides thermals are important to hawk migration, deflective currents. This occurs when air runs into a large surface area like a cliff or woodlands and is deflected upwards, providing a chance for hawks to soar on the rising air.
Hawk migration starts as early as August, with the last hawks trickling through in November (excluding those that can stay well into December like Bald Eagle, Red-tailed Hawk, Northern Harrier, Rough-legged Hawk, and American Kestrel). Peak numbers often occur in September due to the huge number of Broad-wings while peak species diversity occurs in October. On the Hawk Cliff website, there is a species status chart that describes the best times to see each species. There are pamphlets and books available at Holiday Beach detailing identification and status of each raptor species.
In Toronto, I plan to visit Hawk Hill in High Park for the first time this weekend. There have been some good reports coming from the area and mid-late September is peak migration for Broad-winged Hawks. Marianne and I witnessed this first-hand near Pelee where large kettles of Broad-winged Hawks were migrating. Full updates of my trip will be posted. In other news, I am going to have to purchase a metro pass for my new job, which will provide me the opportunity to increase my birding expeditions significantly. My shift also starts at 3:30pm, meaning all of my mornings are free. This will be great to shake off the rust of my fall migration knowledge.