I agree Haz, You're brilliant answer or that of Bobbinwales (peregrines ) fits the clue very well for me.
Personally I would go with 'Peregrines' as they have been in the news a lot lately.
But you're answer about it being a collective noun is spot on.
Matimum has promised to let us know the answer which compiler is looking for once results are published. I think quite a few of us have spent hours trying to find any answer!