Migrating Swallows

Yesterday on my way home from work I saw a large flock of swallows flycatching over the Parmer Lane bridge that crosses Lake Creek. There were about 100 birds. I think they were mostly Cliff Swallows which build their mud nests under this bridge in the summer. These birds have learned to use highway bridges and overpasses in addition to natural cliffs for their colonial nesting sights. There might have been some Cave Swallows mixed in as well, which are beginning to learn the same trick and are starting to expand their range. Today I did not see any swallows as I drove over the same bridge so I guess this flock was on its way north. During the upcoming months keep an eye open for swallows when you drive over this bridge or others. Some of the Mopac overpasses have Cliff Swallow colonies that are huge!