I got this quest: Slay as many birds as you can, and then come back to me for your reward...

You have slain 0 birds so far. I will reward you for a maximum of 10 slain.

But I'm not entirely sure what I should do. I killed big cats (you have to kill big cats except lions). Killed hyenas, elephants, and hypos. But I have never encountered birds. I activated the Snake Scent, but that didn't help me figure out what I should do