Why are there multiple Woodpigeons found dead in and around garden? Are they prone to disease?

We have noticed a few dead wood pigeons in and around the garden of late.  One was hobbling around Saturday night, as if it couldn't quite take flight, unusual seeing them at night. Next day, feathers scattered, head missing and obviously something had got it and made a meal out of it.  Then noticed a couple of dead ones on the road side nearby and then found another dead one in the garden next to the shed today.

The first one seemed to be the usual case of an injured bird that got had.  However these other ones found laying around (all in the last week or so) is unusual.  

Is there anyone that can help identify why this could be happening?  Are there any diseases for example associated with Wood pigeons?  We live in a cottage in a Lancashire rural setting so we are used to seeing them regularly but not dead ones all in a short space of time.  Also, I did think local farmers shooting them but none seem to show injuries to that affect.  

I've attached a few images below if any experts can identify any sign of ailment.

Any assistance would be much appreciated.

Many thanks,

Steve