Why do most falconiforms have a poor sense of smell?

Most falconiforms possess a poor sense of smell because their olfactory chambers are poorly developed. For these birds, the sense of smell is generally rudimentary and holds much less importance than their highly developed sense of sight.12

While most species in this order rely on vision to locate prey, there is a notable exception: the New World vultures (family Cathartidae). These birds occasionally utilize their sense of smell to locate food. This distinction is reflected in their anatomy, as New World vultures possess pervious nostrils—meaning they have an incomplete partition between their nostrils—which differs from the typical structure found in other falconiforms.13