I learned a new word the other day. Irruption. That is a natural event when conditions are favorable for a particular species, and that species responds to those conditions by dramatically increasing the size of its population.
We are having an irruption right now, particularly of red admirals.
I do butterfly surveys over my lunch break. Today I saw 2.4 butterflies per minute. Normally this time of year I see that many in an hour. Seventy percent of the butterflies I saw today were red admirals.
Red admirals perch in the sunlight in the evening, then fly out and chase any other butterfly that goes past. Pairs will circle each other (maybe rivals rather than mates) then land again.
Irruption is a noun. I don’t think there is a corresponding verb. Too bad…