The opposite has happened on my Newchurch Common patch with 7 years ago Collared Doves being absent totally but now seen on 99% of visits. To be fair it's probably just 1 or 2 pairs that have taken up residence so not a population explosion at all. They are still relatively common in the village where I live, Moulton in Cheshire too. But probably now outnumbered in our garden by Wood Pigeons.