Answer:
Your answer would be that "An expert on wildlife" is the appositive in the sentence. This appositive phrase is an adjectival phrase which is considered nonessential.
Step-by-step explanation:
As I've said, "an expert on wildlife" is the appositive in the sentence. Appositives are nouns or noun phrases that follow or come before a noun, and give further information about it. In this case, the appositive renames the noun father. Nonessential appositives add extra information about a noun or pronoun whose meaning is already clear. Therefore, they must be set off from the rest of the sentence with commas. What is more, in this case, the appositive is a complete phrase, as it is made up of a group of words that describe the noun.
Finally, the purpose of the appositive in question is to add extra information regarding the noun "my father".