As far as you can see from within 100 feet of your property. So if a bird flies over the house half a mile from yours but you're in your driveway and see it Count it!

Hearing birds also counts. As long as you know for certin that you are hearing one perticular species you can count it, Such as owls.You must be certin though.

Any other questions?

Thanks for the link Iamarca.
Try this one too

Bird Studies Canada
Raptor