How long do Wood pigeons live for on average?

All of the internet resources I have just read quote an average lifespan of 3 years. What is not mentionned is whether they die at age 3 from natural causes, or from unfortunate accidents involving motor vehicles. I actually 'know' a wild wood pigeon ( :) ), who will fly to my hand for food (for the last 3 years), and my guess is that she is 5 years old at least... I remain to be convinced that the average wood pigeon dies naturally at 3 years old...