Kiwi, a two-year-old budgie, has heard me say "Hey Siri" many times in the house. I never intentionally taught him this, but eventually we started hearing him say "Hey Siri" at random. Later, we started hearing him also imitate the chime that happens after you say "Hey Siri" and let Siri respond. Tonight I caught him activating it on his own. I guess the register of his voice in imitation of mine is close enough for Siri to activate.
家の中で人間が「Hey Siri!」と言うのを聞いていて自然に「Hey Siri!」を覚えたそうです。