It's a sad fact of life that Tree Swallow do not fledge if they are being stared at. So my advice is to put out of your mind the whole idea of spending a hot afternoon watching a small hole. Don't concern yourself with the possibility of sadness, don't let worry mount your imagination with stark images of failure, and go find something more useful with which to pass time. And do not let adult Tree Swallow tempt you with their play acting that something like fledging is about to happen, because Tree Swallows are cocky and deceitful little bastards. Oh, they'll fly around and call and give off every symptom of a parental desire to share flight with off-spring. And don't allow yourself to ever say "Maybe if I wait three more minutes I'll see the little fellows make their first flight," because Tree Swallow can hear those kind of thoughts, and they call loudly to their nest, "Not yet."
So you come to your senses and you go inside, because your head aches, and you
can hardly see because despite the sun glasses your own mental apparatus is
recording spots and flashes, and you think maybe this is what Rapture will be
like. And your peripheral vision has been so reduced by blue sky you fall
over the bloody de-humidifier, damaging an already damaged shin and
sending a splash of water across the floor, which requires instant clean up
otherwise wood eating mold starts to grow and there's the risk of electric
shook, which would at least be a quick way to end it all. Then, despite the risk
of heat exposure and the possibility of precipitating yet one more near death
experience you go outside for a cigarette, and there they all are, on the
electric line. And it might well be a relief to see everybody safe and
whole, but far better all round if they at least pretended not to be
laughing at you.