We went with friends down to Pelee and walked out to the tip that isn't there anymore. It comes and goes depending on what Mother Nature is up to.
Migrating and wintering Tree Swallows can form enormous flocks numbering in the hundreds of thousands. They gather about an hour before sunset and form a dense cloud above a roost site (such as a cattail marsh or grove of small trees), swirling around like a living tornado. With each pass, more birds drop down until they are all settled on the roost.