So apparently these swallows have adapted to our modern bridges to use them as an excellent place to raise a colony.
For many years I noticed they were struggling with those darn English Sparrows. The enclosed mud nests are the perfect place and size hole for those invasive and aggressive sparrows to take over the nests.
So for many years the swallows moved from one concrete bridge to another. There are 3 in our bottom...
Then a few years later I noticed the swallows had moved to the East Street bridge by Willow Creek.
I was glad they continued to colonize in this area, but sad they weren't on our bottom road.
Then after only a year or two along Willow Creek they moved back to the bridges in our bottom, which I'm happy about because they are great at catching and feeding on flying insects.
I hadn't inspected their nests for about 5 years and was amazed when I saw how they have really taken over the outside concrete beam.
During prior years they made nests in a more hap-hazard way on the beams underneath and not all in a row.
I think they figured out there is safety in numbers by mostly nesting together as shown below.
Those darn English Sparrows, which are NOT native, but brought over by some of the Pioneers a long time ago, are not as much of a threat when the swallows colonize this way.
I also have an aggressive trapping process to catch and reduce the English Sparrow population on our farm.
I've been doing this to help the Bluebird and Tree Swallow trail I've been maintaining for around 40 years.
As I'm writing this article, I continue to reflect on the number of bird and other animal species we have now that did not exist here when I was a kid...including those darn deer that have really adapted to the changes we've made to Iowa's environment and have become very fruitful and multiply.
Bird species we have now but didn't see when I was a kid: Turkey Vultures, Kestrels, Cliff Swallows, Bald Eagles, Asian Doves, and several more I can't think of right now...
I would guess the reason why some nests have fallen off or broke apart is from the vibrations created by the heavy truck traffic...but for the most part the nests appear to be "hanging in there..."
Cliff Swallows swarming around me
I don't think the swallows felt threatened by my presence, because they didn't attack me like some birds do when they perceive their nests are threatened, but they definitely were annoyed with me.