Mark Armstrong, master bander of both songbirds and hummingbirds, and his wife Janie Kading, have a chimney swift tower that Mark constructed in their back yard
For several years swifts have nested in the tower. Small holes are drilled in the bottom of the base so that you can look up and actually see how many nestlings have their heads over the nest edge and how many swifts are roosting on the chimney wall.
This breeding season a pair of chimney swifts raised at least three young in the tower. The nests are shallow and when considering its small size, it is hard to imagine how three nestlings can fit into it. Both the male and female bring sticks to build the nest, breaking them off with their feet and carrying them to the nest site in their beak. The twigs are then sealed with sticky saliva from the swift's seasonally enlarged sublingual glands
Even more fascinating is the description found in the account of Birds of North America notating the timing of egg-laying. "Egg-laying begins when nest half-finished at about 3-6 d, and new twigs and saliva added during incubation...." The pair stops adding sticks shortly before the eggs hatch.
On July 1st, Mark and Jane set up traps to capture and band hummingbirds in their yard. In addition, to the hummingbird traps, a mist net was set up to capture hummingbirds and possibly a swift as it left the tower after feeding young.
The swift's interesting tail structure also is clearly an additional support while roosting. The feathers end in sharp barbs that help to support the bird while clinging to the roosting surface.