Hi MOBirders:

For the last few years, during breeding season, I've noticed at least a pair, sometimes 3 or 4, of NORTHERN ROUGH-WINGED SWALLOW flying around in a very small, isolated area of my work campus in St. Louis County.  I would see them every day in the same place, more or less.  It was apparent they weren't just passing thru.  What were they up to?
I know where many of the local Barn Swallow nests are and the location of the Western Kingbird nests.  I thought the swallows might be nesting but I never figured out where.  At first I thought it was an old outdoor equipment shed.  That eventually got boarded up tight but the birds stayed nevertheless.

Well, on Monday the birds themselves gave me a clue.

I saw 2 swallows land on the asphalt pavement underneath the head of a semitrailer parked in long-term storage, put 2 and 2 together, and supposed they are nesting in the trailer.  I looked underneath several parked trailers and found nests under two trailers.  I stayed for a few minutes, watching the birds from a distance and, sure enough, 2 swallows zoomed up to the underside of a trailer and disappeared.

On these particular trailers there is framework supporting the trailer boxes above but there are oval cutouts opening to narrow spaces between the frames and trailer floors; just enough space to maneuver and build nests.  The bottom of the nests are hanging down out of the cutouts.  

Cornell BNA Online describes NRWS nest site preferences, which are pretty diverse, and the description even includes "semitrailer."

Mike Thelen
Univ City, StL Cnty, MO
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