kinda a fictional species. in my ocs universe there are angels whos job is to make sure everything is in order and there isnt anything planet threatening. angel whisltes job is to look out for these types of stuff and call over angels by whistlying . angel whistles dont all look like this, they mostly take a bird form and head that can perfom as an whistle, as you can see that this one look more like an owl, as they are really quiet when flying, so as soon as it will see anything that needs to be handled by an angel it will whistle and quietly fly away to not be seen or heard by the threat.
i might draw more of this species birdies someday, but they have to be not really bright in colors and really fast flying or really quiet.
the whistle sounds is a really loud, low sound so it could be actually heard by an angle .
angel whistles are around human sized or bigger.
they are passive, consume the stuff what the bird that they are based of eat.
for example this angel whistle when eating will split its "mask" and reveal a teethless mouth, as it has one in the centre eye it will just pull back into its head when the mouth is open. if the thing its eating is small enough it will just swallow it whole but if not it will tear it into smaller pieces for easier consumption.

im sorry if this unreadable, im not good at explaining stuff and english is my first language, sorry!!