Is there a homonym for tern?

Yes, there is a homonym for "tern". It is "tern" itself, but with a different pronunciation and meaning.

* "tern" (pronounced like "turn") refers to a type of seabird.

* "tern" (pronounced like "turn") can also be a variant spelling of "turn". For example, "take a tern" instead of "take a turn".

While the spelling is the same, the different pronunciations and meanings make them distinct words.