Falcon, little larger than a Kestrel, chasing a bird, sounds like it could have been a Merlin.
Spring firsts:
Common Grackle, Mar 6, Onion Fields, Point Pelee
Red-winged Blackbird, Mar 6, Hillman Marsh
American Robin, Mar 11, Chatham
American Goldfinch, Mar 9, Chatham (Haven't seen them earlier this year)
Tundra Swan, Mar 10, Chatham (migrating north)
/Thomas