Barn Swallows build their nests almost exclusively on man made structures (allaboutbirds.org). Indeed we saw a few examples of that while we were walking around the bird sanctuary in mid-May. The nest in picture above was built in quite a high traffic area, right on the warming hut.
We caught the Barn Swallow below adding some materials to their nest in a covered observation/lookout just off the west field. (I just shot two shots and vacated the spot as this Barn Swallow wasn’t too happy to see me there).
OTHER POSTS FEATURING THE BARN SWALLOW: