I know you have all been wasting a lot of mental energy pondering this hugely important question…and likely to no avail.
Well, wonder no more! Finally, someone has done it! I have slowed the birds down 400% (that’s 2 octaves…someone had to do it!), and to be honest they sound a little odd.
(For reference, here is the original audio. It was used in my song in the previous post).

When they were slowed down a bit less, they sounded like chickens, but now they sound more like monkeys.
If you slow them down one more octave they start sounding like Klingons.