mystery whistling bird in water meadow

 I wonder if you could help... very few bird guides / websites give information on behaviour of birds; they usually concentrate on physical characteristics. I wonder whether you know of a site that allows one to identify a bird by its behaviour, e.g. flight pattern, foraging guilds/ activity, its association with other birds - also its often different winter behaviour and tendency to form foraging flocks with other species.  This would be so helpful for partially sighted people.  

An example: I disturbed several times the same species of bird  whilst walking along the Bure [near Blickling, Norfolk] in a water meadow . It flew up with a startling whistle from the edge (or the middle) of the river and flew off in a zigzag fashion - far enough so one could not see where it landed again. It seemed to be a grey bird - but this was only the impression of a second. 
I first assumed it was a duck; but the only whistling duck in Britain is a wigeon, and they live in winter flocks [I believe]. This bird was definitely on its own, although once, another bird [mate?] about 50 meters off flew away a minute later. I don't know of single whistling waders that live inland during the winter either. Sound recordings of snipe alarm call confirmed that it was not that what I had heard. when the bird took off in flight. 
I would be very grateful if you could give me your opinion!