This is an X ray of Tomo, a bird of prey who ended up at a rescue centre as he had been shot. You can see the lead shot, the white dot on his wing. We deal with pets being shot too, but this is usually by airgun pellets. Air guns do not require a license and once people have mastered shooting at targets they want more of a challenge and unfortunately a cat wandering through the garden is the next step.
With wild animals it is normally guns that need a license that are used. Sometimes they may be used legally but if the animal is not killed but wounded it can end up at the vets. Often, I suspect, they are used illegally to shoot at wildlife as in the case of Tomo. Wildlife that is injured such that it cannot be released into the wild again either has to be fostered, which can be difficult, expensive and not always fair on the animal, or put to sleep.
There have been several attempts to make airguns restricted but so far they have failed.