Little Egrets arrived naturally by range extension, though: a twitchable bird on Merseyside in the late 80s, they began overwintering on the Dee, then the Ribble. There's a spectacular Little Egret roost throughout the year now on Southport Marine Lake; this last winter joined by a Great White Egret too: there are a few of these around and they're likely to be the next to extend their breeding range. Avocets also returned naturally, having become extinct in UK.
Little Owl is an introduced bird, from France, now on the British List for over 100 years. The really contentious one of course is Eagle Owl - once indigenous but became extinct, escaped birds in Yorks and Bowland have established a few years of successive wild generations, and the culling debate there is fierce! Ruddy Duck - which can hybridise with White-Headed Duck (nearest population Andalucia?) - were subjected to an EU directed cull in recent years. Ring-necked parakeets are now far too well established here and throughout Europe (and Rose-Ringed) On Merseyside they're in Sefton Park, Southport Botanic and there's a very well established 5th or 6th generation population across the Ribble in Lytham St Anne's cemetery that will soon spread.
