He is an expert in ecology.

He is very interested in ecology.

He found a small animal's burrow in the forest.

The Eurasian jay is a bird that is widely distributed in Europe and Asia.

Where is the Tengu nest?

There is a beautiful nest board in my garden.

Transitive verbs require an object that is directly moved by the subject.

He has a very passive personality.

He always acts as if it's someone else's concern.

He passionately discussed the problem of other minds in his philosophy class.