I've been photographing nesting Cedar Waxwings and I have to say that it tests my skills and is a true challenge because of the light, how quickly these birds move and the cluttered habitat.
While I photographed nesting House Wrens in the High Uintas the last day of May I also photographed Tree Swallows that were nesting in the same Aspen tree in a cavity a bit lower on the trunk.
Two days ago I spent time photographing nesting House Wrens in the high Uintas near Mirror Lake Highway, of interest to me is that two years ago I photographed Red-naped Sapsuckers using this same nesting cavity.
Barn Swallows are like tiny, feathered brick masons. One pellet by itself is nothing but combined pellets form the nests these birds use to raise their young in.