A Neighing Horse ?

Several times now I have heard a neighing horse in the distance, I presumed a neighbour had acquired a horse. Today , I could hear the neighing horse in the 70ft high tree at the bottom of the garden.

It was very well camouflaged, its call was load and clear, then I could hear the same further away. When I saw the bird fly off it looked very much like the bark of the tree.

What is it, is it native to the area ? I reside in the West Midlands, never heard of or seen one before.