Birds are tetrapods but though their hind limbs are used for walking or hopping, their front limbs are wings covered with feathers and adapted for flight.
bˈɜːdz ɑːɹ tˈɛtɹɐpˌɑːdz bˌʌt ðˌoʊ ðɛɹ hˈaɪnd lˈɪmz ɑːɹ jˈuːzd fɔːɹ wˈɔːkɪŋ ɔːɹ hˈɑːpɪŋ, ðɛɹ fɹˈʌnt lˈɪmz ɑːɹ wˈɪŋz kˈʌvɚd wɪð fˈɛðɚz ænd ɐdˈæptᵻd fɔːɹ flˈaɪt.