SB 11.20.15
chidyamanam yamair etaih
krta-nidam vanaspatim
khagah sva-ketam utsrjya
ksemam yati hy alampatah
Translation:
Without attachment, a bird gives up the tree in which his nest was constructed when that tree is cut down by cruel men who are like death personified, and thus the bird achieves happiness in another place.
Purport:
Here the example is given of detachment from the bodily concept of life. The living entity resides within the body just as a bird dwells within a tree. When thoughtless men cut down the tree, the bird, without lamenting the loss of its previous nest, does not hesitate to establish its residence in another place.