Birds from beneath can look blackish or gray (especially males) and brown or brick-red (females) variously.

[3][4] Tree snails (e.g. Bulimulus, Homolanyx, and Polymita) are a vital component of the hook-billed kite’s diet.

It has also been observed that the beak of the hook-billed kite has adapted in size and shape between different regions of their territory in response to the species of tree snail available to them.

[11] When it finds a tree snail it holds it with its talon and uses its beak to pry open the shell.

This raptor is often considered sluggish and retiring, preferring to perch inside leafy canopy when not flying.