The original clutch size of this chimney swift pair was never known to us, however shell fragments from at least two eggs were found below the nest on the barn floor. One well feathered young (not able to fly yet) clings precariously to the wall. Note the sharp tail feathers that act as a brace for support.
Young swifts were so tightly crammed into this nest when we visited it last Sunday, it was impossible to be certain whether all 4 eggs had hatched. Today all 4 young swifts were visible with 2 out of the nest and 2 others still in it.
Swift research 'gold'. 4 breeding years of swift poop heaped on a timber, several feet under the active nest with shell fragments and a history of insects ingested by young during that time.