Fifteen minutes, once, on a sunny day between July and August
What to do
Pick a sunny spot, watch for fifteen minutes, and count the butterflies you see. A chart of eighteen species is on the page.
When
Any sunny day between mid-July and early August, between about eleven and four. Butterflies do not fly much outside that.
Why it matters
Two of the eighteen species have declined by more than half in twenty years, and this count is how that was known.
