Bird back blips

A birdhouse swings from each end of our covered porch. Some years they are empty, but this year chickadees nested in both of them. Because of the angles and height, taking photos is quite difficult, and the results are not particularly clear, but we can basically see what's happening. 
A few weeks ago we watched the adults flying around checking out the houses, and today was the first day that I could tell that the chicks had hatched.