In a recent post, I talked about a bird nest on our front porch that used to house Barn Swallows (Hirundo rustica), but that this year was commandeered by an Eastern Phoebe (Sayornis phoebe). I had mentioned that I wasn't sure whether this nest was initally created by Barn Swallow or Eastern Phoebes. After that post, I discussed this topic with Kirk Roth at the Loblolly Marsh Bioblitz. Kirk told me that it sounded more like a Barn Swallow nest, as Eastern Phoebes create nests that are supported by a structure underneath them because they don't use as much mud as a Barn Swallow. The mud holds the nest to a vertical structure, allowing it to be created without any supporting structure beneath. Barn Swallows will also create nests supported by a structure underneath, but their nests are still made up of more mud than an Eastern Pheobe nest.
I mention this because my coworker, Robert Wolfe, recently sent me an excellent photograph of a Barn Swallow nest from his barn.
In the photograph, you can see six near fledgling Barn Swallows (notice that there is a sixth bird second from the right, with only the beak showing). Females can have up to seven offspring at a time; that's a pretty crowded house! You can see that the nest is identical to the one on our front porch, with the exception that the Eastern Phoebes had added a moss layer inside the nest. There is nothing supporting the weight of this nest except the heavy mud caked to the side of the barn. Rob tells me that the nest is just 7 feet up and in the most heavily used part of the barn. Therefore, these birds are pretty tolerant of human activity close to the nest. In fact, Barn Swallows have thrived around humans and became more abundant as humans spread throughout the world. Humans, in turn, have benefited from these insectivorous birds near dwellings. I remember when I used to mow baseball fields during the summers, and thought that the Barn Swallows and Tree Swallows were swooping at me... instead, they were swooping to feast on insects that I was kicking up with the mower.