Northern Rough-winged Swallow - Photo by Ron Payne

Northern Rough-winged Swallows are not an uncommon sight at Wright Park in Middlebury, so when walking there recently I was not surprised to find a pair flying near a field there. What did surprise me though was to find out exactly what it was they were doing. Before European colonization of America, Northern Rough-winged Swallows traditionally nested in burrows or niches in rock near water, but since our arrival many of them have taken advantage of man-made structures such as dams and bridges to build nests in. I know of a colony of nests built into drainage holes on the side of a building at the nearby Belden Falls dam and always assumed that the Northern Rough-winged Swallows I was seeing at Wright Park were the ones nesting there. However from that field in the park you can see a storage trailer facility that is located on Industrial Avenue, and as I watched the swallows, their activity seemed to be focused on that facility. One was flying into a propane tank enclosure, picking up nesting material and then flying to one of the semi-trailers parked there and disappearing from sight. It repeated this process a few times but I could not see exactly where the Swallow was going. So after completing my walk at the park I drove over to the storage facility to see if I could get a better look.

When I arrived I saw not one, but two pairs of Northern Rough-winged Swallows engaged in bringing nest material to the trailers. From this vantage point I could see that they were entering the underside of the trailers at the front. A closer examination of one of the trailers revealed a series of holes approximately 8 inches in diameter cut into the steel plate through which the birds were entering, and though I was unable to see the nest itself, it was clear that this was indeed their nesting site. I later looked online to see if this kind of behavior had been documented before and found an article from 1988 that has a very similar description as well as a few other more recent accounts. It’s a very opportunistic but risky location to build a nest as there is always a chance that the nest site will be hooked to a truck and driven away, but since these trailers seem to be used for long term storage that does not appear to be an issue.

– Ron Payne

Storage Trailers

Nest Holes