 The strongest attacks are based on embryological analyses that conclude that birds' wings are formed from digits 2, 3, and 4, (corresponding to the index, middle, and ring fingers in humans.The first of a bird's three digits forms the alula, which they use to avoid stalling in low-speed flight—for example, when landing).The hands of coelurosaurs, however, are formed by digits 1, 2, and 3 (thumb and first two fingers in humans).