The unfurling of a crocus is all that it takes for me to believe that an invisible line has been crossed in the progression of the seasons. Winter might still hold all of the trump cards, but Spring has peeked over the parapet and has taken a look around.
After spying that crocus, I spent an hour at Priest Hill and was delighted to hear up to four Skylarks in song and display - the first this year. This species has been otherwise sullen so far. A Common Buzzard also crossed the airspace (the first since early autumn here) and drew an escort of corvids that frantically and noisily chased it away. We have quite a marked Spring passage of this raptor, and I wouldn't mind guessing that this is an early migrant.
We may still see snow, frost and freezing cold, but the next season in line has already put a marker down.