Quote from : The Pale King Book

...it occurred that the birds, whose twitters and repeated songs sounded so pretty and affirming of nature and the coming day, might actually, in a code known only to other birds," be the birds each saying 'Get away' or 'This branch is mine!' or 'This tree is mine! I'll kill you! Kill, kill!' Or any manner of dark, brutal, or self-protective stuff--they might be listening to war cries. The thought came from nowhere and made his spirits dip from some reason.