I was on AC503 yesterday which murdered a couple of birds. We in the middle of our ascent when there was a pretty strong burning smell in the cabin. Sometimes you get an oil/fuel smell but this was much, much stronger. People were reaching for the fan controls. After a bit the captain comes on and says we've hit 2 birds. One on the windshield and one into the engine. Everything "looks normal" but we're going back to YYZ as a precaution. Turned around and landed with the fire trucks and everything to check us out (for flaming bits?) before they allowed the plane to go back to the gates. When deplaning you could see a lovely red smear covering 1/4 of the windshield.

To AC's credit, they were very organized and swapped the next flight from a E190 to an A321 and accommodated everyone.