To look for sounds which might become a reliable way to protect aircraft from birds is an interesting topic.

But I don't think it works for greater ditances - what it should because of the high speed of an a/c.

I have watched birds which were circled by a peregrine. As long as the peregrine was near to them, they had no panic at all and they didn't abscond.
The reason is: the peregrine is a very slow flyer when it flys horizontally.

Only when the peregrine falls from the sky vertically other birds go into a spiral descent and try to reach trees or other shelter (if they notice it soon enough).

birds can not hear nor produce ultrasound!

Their audible (and vocal) range is from 250 up to 4000 hertz.

That's why we can hear them twitter.

This would be a useless attempt then.