There is a Lull in the purple Martin season between the craziness of spring pairing, nesting, and claiming compartments to the time feeding becomes a full time job for the martin parents.
This lull is a time that morning activity decreases but most noticeable is the decrease of evening activity This is the time of incubation. The female Martin is usually on the Nest while the male goes about foraging and keeping watch over the cavity. The time the female is off the nest is short and she quickly returns to the eggs. I think this lull has part to do with not drawing attention to the nest and is a protective measure. And part to do with the priorities of survival
Once hatching begins and feeding become almost constant, the evening activity begins to increase. It is a relaxing and enjoyable time to watch as beak full after beak full of insects is brought to the cavity for hungry and fast growing purple martin babies.
Soon young will be fledgling and the days will become more silent, replaced by the fun and excitement of the returning birds in the evening.
