New nest or old nest?

A group of wild-buffaloes were resting under a mango tree at noon when they found a crow bringing dry leaves and grasses to build its nest. One buffaloe in the group asked the crow why it was building a new nest when there were so many abandoned and unclaimed nests available in good condition all over the forest. A fox nearby on hearing the buffaloe's question laughed and said the crow must be really stupid for working so hard to build a new nest when so many other nests were available for free. The crow felt irritated and insulted by the fox's comment and said,
" I can't use other nests because, I didn't build them, hence they are not mine."