Wiktionary
decurved
a. curved downward
WordNet
decurved
adj. bent down or curved downward; "the decurved bill of a curlew"
Usage examples of "decurved".
Though ornithological writers are almost unanimous in distinguishing the buzzards as a group from the eagles, the grounds usually assigned for their separation are but slight, and the diagnostic character that can be best trusted is probably that in the former the bill is decurved from the base, while in the latter it is for about a third of its length straight.