Usamah bin Zayd (may Allah have mercy on him) said: I was present with Umar bin Abd al-Aziz (may Allah have mercy on him) when he was ordering that the flying (racing) pigeons be slaughtered, and those with clipped wings be left.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20942