I understand that.
The BBC had a programme tracking ospreys a while back. A couple of them just flew to completely unexpected places (more than 500 miles from where they were expected), the more normal ones were much more random than expected too. No one could really figure out why they flew to the places they did when they did.
Had there been some kind of problem where the ospreys were not, it would have been all to easy to assign knowledge to the Ospreys.
Also, as I said above : Plenty of animals do get killed in natural disasters, migratory birds are _very_ affected by storms.