Hume's Leaf Warbler breeds from Central Asia into China and migrates south for winter. The HKBWS account says most Hong Kong records are of subspecies mandellii.
The nominate subspecies humei has a slightly darker bill and legs and colder plumage tones than mandellii, including less bright green fringes on the flight feathers.
Small invertebrates are sought among branches and leaves. A small number winter in Hong Kong and use forest habitats there.
An extinction-risk assessment has not been added yet.