For modern birds, the condition varies somewhat. None have more than one
phalanx on digit III, though I'm not sure how many lose this phalanx. Only
a few birds are known to have unguals on digit II (natal anseriformes, the
hoatzin, occassional specimens of natal Circus, natal Otus, Rallus, adult
Corygyps). Manual unguals on the first digit are usually found in basal
orders (galliformes, anseriformes, 'ciconiiformes', 'gruiformes', gaviids,
falconiformes, strigiformes, charadriiformes) but never in a lot of the
"higher landbirds" (columbiformes, 'coraciiformes', trogonids, piciformes,
passeriformes).