Last year I found one nesting in the barrel of a cannon on the Monocacy  
National Battlefield. It was feeding young. I watched 3 cycles {return about  
every 6 minutes}, and after leaving the 3rd time I went to the cannon and  reached 
into the barrel -- I couldn't touch the nest -- must have been close to  the 
end of the barrel -- I marveled @ the parent flying in at, perhaps 20 mph!  
From Kenn Kaufman "nest .. sometimes in cavities, such as drainpipes, culvert,  
crevice in bridge support, hole in side of building .. Nest at end of burrow  
..
 
Gary Smyle 
Frederick
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