What atmosphere layer do birds fly in?

Birds fly in the troposphere, which is the lowest atmospheric layer.

Simple the troposphere which is where birds fly, clouds develop and pollution collects.

2cool and cold temperature unless its an ever green tree 

Nestor foreshadows the plan of the suitors to kill telemachus through his account of what happened to agamemnon who was murdered by people around him. despite this telemachus was reassured that his voyage was going to be safe with the of athena.