Jackdaw---strange behaviour

On the opposite roof, much watched ! Today I was upset to see a Jackdaw lying on the roof with another next to it ?? Quickly grabbed my binoculars and watched. Other Jackdaw moved away and I noticed MOVEMENT !! but only to now splay another wing.???Dying,but no, raised head and slid forward.I watched 20 minutes and in that time it moved forward 4 times and then suddenly stood up,ruffled its wings,poked a beak under the wing and FLEW OFF ! Was it lying on the hot roof for health reasons ?? Any ideas ??