Osprey 

Along the river I occasionally hear an Osprey's call.

 Here (click) is a link to information which includes the characteristic call of the bird, sometimes referred to as the Sea Eagle.

The call is unexpectedly plaintive for a bird of this size. I have seen one diving, in its strange, crashing way, for fish in the Raritan. The Osprey, not to long ago, was considered an endangered (click) species in New Jersey.