Ospreys - or Fish Hawks - are flying fisherpersons. They are rather serious food gathering types who grab and go with most anything that can pass as a fish. From observation, it seems unlikely that such birds have a preference for perch over trout. Certainly, their offspring do not seem to care as the forminable hook on the beak breaks and opens fillets and fillagree without bias.
With marvellous unbaited hooks and grippers (called feet in lesser birds), and the diving ability of a falcon, they can grab onto and hold otherwise slippery, slimy and squirmy fish.
This work explores - and attempts to suggest - that it is entirely possible that an Osprey can latch onto something that it cannot actually lift. The tilt to the bird and prey suggests that they are at a kind of go-no-go stage in the drama. While the marvellous talons and spicules can grab and hold, it may be very difficult for the bird to let go afterwards. Unfortuately (for the bird), drowning can be the consequence.
