I expect this is an easy one!
On the last 2 rides which have taken me into upland moorlands, I've wondered what these are.
Habitat is upland moorlands, so probably ground nesting.
Locations were: Approach to Lecht from Tomintoul, and moorland around Redstane Rigg.
Medium sized, perhaps size of a small pidgeon or similar.
Black when viewed from above, but when seen from below, white underbellies and wing patches.
Very characteristic flight: swooping down to the ground, just missing it, and swooping up again. Usually in pairs. Repeat this dive-bombing several times, before finally landing and sitting down.
Also very characteristic: The tops of their heads seem to have a tall crest that curves and hooks forwards towards the top.
Wot is it?