It's at this time of year that I can't help myself - I go all phenological in the garden. (I like the word, even if Spellcheck doesn't).
'Phenology' is the study of the season cycles of plants and animals; it is now, in spring, more than any other time that I find myself watching the sequence of events that mark the accelerating march towards summer.
Some of it is indicated by the birds - the first chiffchaff, the first swallow, the first cuckoo and the first swift, normally in that order. In the past, you could have inserted turtle dove into that list (in lowland England and Wales at least), but few of us have that privilege now.
Butterflies are great at signalling the seasons too, with orange-tips, speckled woods and holly blues being the most recent 'emergents' (it's another new word for Spellcheck).
I though it so nice that I wanted to share this lovely opening comment from the RSPB gardening tips for May.