Jays take flight from roving squirrels
My source for this information was David Cabot’s excellent book Irish Birds. In it he writes: “The jay has apparently been extending its range northwards and westwards since the beginning of the century, while becoming scarcer in the south-east, where its absence from suitable breeding habitats is difficult to explain.”
Although my copy of the book is dated 2004 the first edition came out in 1995, so I was pretty sure that the century he was referring to was the 20th not the 21st .