"The Windhover" is about the speaker's admiration for a beautiful bird, true. But it also touches on some bigger philosophical questions—like how even boring, everyday objects can appear beautiful and amazing if only we know how to look at them in the right way. This poem is partly meant to show us how to open our eyes to see the beauty hidden in everyday things.
The windhover appears beautiful because of the speaker's ability to see beneath the surface.
It is actually the surface beauty and power that the speaker admires in the windhover, rather than its hidden qualities.