פירוש על עבודה זרה 84:3

The question in this baraita seems to be whether one may use the bird’s nest to make a fire (I know, not a nice thing to do, but people needed firewood back then). If the tree has been dedicated to the Temple, then we could assume that the branches may have been dedicated. One should not therefore use them. But if one does, this does not count as “trespass,” illegal use of Temple property because we cannot be sure that the nest came from that tree.
But if the tree was an idol, then one can use the nest. This proves that pieces broken from an idol are permitted and refutes R. Yohanan.