Well, let's say during a siege, they can do a lot... they can deal with those who got inside and stand guard at the gates if needed.
I'm not arguing that they can't. It's just that their speed doesn't appeal to me:confused: In my opinion, the birds are stronger, faster, and more effective. :) The monsters might be more reliable, but...
and during an assault... a lot depends on various factors... for example, on teleportation magic (if available), and in general... birds won't do much during an assault either... you wouldn't throw them in alone, would you?
Of course not alone... But with birds, you don't have to waste an extra turn on a Teleport, Speed, Flight, or some other spell...
;)