Nesting and keeping close to their nests, perhaps. I always have about a month of intense activity during April, and then it slows down considerably for several weeks, only to pick up again. This process repeats several times. Also, activity is reduced on very hot days, peaking in early morning and late afternoon, and whenever it rains. They were drinking 1.5 liters of solution a day last week, but today, maybe a fourth of that.

No sighting for a week now. The air is full of bugs and of course flowers are blooming. I've read they prefer "natural" diet to the sugar water. Maybe that is why they aren't at the feeder, although I haven't seen/heard them zipping through the air either.