Dead pigeons are generally seen as a bad sign if you believe in such things.
Pigeons and doves are very symbolic and represent a lot of things most notably peace, purity and wisdom.
The death of a pigeon can mean the death of peace, the death of purity or the death of wisdom.
Another belief about dead pigeons which is common in South America is this..
..if you find a dead pigeon by your doorstep there is a belief that you have been cursed, however the pigeon has blocked the curse and died on your doorstep as a result.
In more practical terms a dead pigeon probably doesn’t indicate a great deal other than that the pigeon has had an unfortunate run-in with a cat, dog, car or other predators…or has simply reached an age where it’s time has run out.