Underneath the new 13th Street bridge in Columbus are nearly 100 mud swallow nests like these. The Riverwalk on the Alabama side of the river goes underneath the bridge, so I had been passing these nests every time I walked down to the rapids to photograph the blue herons. One day I stopped to eat lunch under the bridge and to watch the swallows. It turned out that many of the birds I saw flying in and out were not swallows, they were English sparrows. I knew what a nuisance they were but until I went home and looked them up on the web I never realized how aggressive they were in stealing other birds' nests and usurping their territory.