every creatures have been already programmed to perform their activities systematicaly till the day of their survival as per the command of God Almighty. So, not only the birds but also tiny ants they have their organization set up and type of life style that they make, they discuss each other in their language and coordinate together and react asper the situation as I envisaged above and asper the feed back of Almighty.
See in You Tube Buffallow vs Lion., and many other animals, birds, snakes and watch the way they live and move and they have all programmed. It is mentioned in the Quran very clearly in arbic word., (Khalaqa thumma hada). about this phenomenon. good luck.