Why can't birds figure out the reflection is not another bird?

There was a hummingbird hovering outside our glass door last week. We were trying to decide whether it was looking at itself or the reflection of the flowers behind it. It left and came back several times.

Dumb people aren't called birdbrains for nothing...

Narcissist birb

There are quite a few animals not clear on that concept. But one of the apes (I can’t remember which one) differs in perception from any other non-human; if you point, it will turn and look in the direction you’re pointing.
Every other animal will just look at your finger. 🤔

Same reasoning humans cant figure out hating others is wrong but keep doing it