Musnad Ahmad 31:6

Hashim narrated to us, Yazid ibn Abi Ziyad informed us, Abd al-Rahman ibn Abi Nu'm al-Bajali narrated to us, from Abu Sa'id al-Khudri, that the Prophet, peace and blessings of Allah be upon him, was asked: "What may the *muhrim* (pilgrim in ihram) kill?" He said: "The snake, the scorpion, and the 'little corruptor' (the mouse). He may throw stones at the crow but not kill it, and [he may kill] the biting dog, the kite, and the predatory beast that attacks."