Answer: The adverb in the sentence is "yearly".
Explanation: An adverb is a part of speech that is used to modify a verb, an adjective or another adverb. An adverb generally makes reference to how, when, where or to what extent something happened. Moreover, many adverbs end in "-ly". In this sentence, "yearly" ends in "-ly" and it is describing a verb ("migrate"). Furthermore, "yearly" is an adverb of frequency because it has been used to express how often Canadian geese migrate.