A pair of barn swallows (Hirundo rustica) had a nest on our back porch and successfully fledged four chicks in June. (See 2016 Barn Swallow Fledgling 06-27-16). They, or another pair, built a second nest under the eaves of the back porch. All four eggs hatched.
A heat wave arrived soon after the chicks were born. Afternoon temperatures soared over 100° and it was much hotter under the porch eaves. The parents often sat on the edge of the nest panting. I noticed that the parents fed the chicks less often and the chicks were lethargic. Then I found one chick under the nest. It was alive but not developed enough to have fallen out itself. Leonard placed the chick back in the nest and soon it was on the porch again. After several days the parents disappeared. Checking the nest we found three dead chicks.
Either the extreme heat killed the chicks or the parents were unable, because of the heat, to adequately feed their brood – or both.
The picture was taken through my kitchen window (Lookout CA) of a parent feeding one of the doomed chicks.
Not all stories in nature have a happy ending.