Bird poo ball

Hi,

I have found a massive ball of what looks like bird poo but was wondering whether anyone can shed any light on it? I have never seen anything like it, bit bigger than a golfball in the middle of the courtyard. I am not well up on birds (but trying to learn), but we do have tons in the garden including wood pigeons, collared doves, coal tits, blue tits, bull finch, goldfinch, sparrows, dunnocks and tons of Starlings that come daily. Have had a sparrow hawk and from the dusty imprint left on one of the windows - an owl of some kind. But this doesn't seem like a pellet, its really squidgy and poo like (can't see any bones or feathers, poked with a stick Joy).

Any suggestions gratefully received (I am most concerned it is some sign of illness).