I wonder how many birders of today remember twitching a bird that has now become one of the commonest garden birds in the UK. It was first recorded in Lincolnshire in 1952 and bred in Norfolk in 1955 and by the production of the first "Atlas" (1968-72) it was recorded in 69% of the UK's 10 km squares. with an estimate of 30-40,000 pairs.The distribution has now reached 83% with a population of around 990,000. The spread across Europe was no less remarkable. At the beginning of the 20th century it had a foot hold in Europe in Turkey and parts of the Balkans. It arrived in Hungary in 1932, Czechoslovakia in 1936, Austria in 1938, Germany in 1943 and the Netherlands in 1949. It didn't stop in the UK and wild birds have been recorded in Iceland and possibly the USA but introductions muddy the waters. I guess in 50 years time we will be at home with all the Southern Herons that have and are now colonising the UK, but I wonder how many species that were the staple diet of my birding youth with still be with us. The first article in British Birds on the spread of the Collared Dove was in Vol 58, no 4, 1965.