Beth Kantrowitz asks about Northern Rough-winged Swallow nesting
habits: 

> My question is, do Roughies make their nests against 
> walls like other swifts and swallows?  I'm trying to 
> figure out if the egg I saw was in a nest or if it was 
> a dud egg pushed out of a nest by an adult.  Is it too 
> late in the season for unhatched but viable Roughie eggs?  

According to Ehrlich, Dobkin, & Wheye (The Birder's Handbook), the
NRWS's nest is at the end of a burrow or drain pipe 1' to 6' deep and
made of "grass, leaves, weed stems, and occasionally moist horse
dung." (not a pretty picture)  The eggs are white and unmarked while
cowbird eggs are white to grayish-white with brown speckles.  It might
possibly be that you saw a cowbird egg that had been pushed from the
nest by a savvy adult.

The eggs are incubated for 12 days and then the young fledge in
another 19-21 days after feeding by both adults.

According to the Yellowbook, the earliest egg date is May 13 and the
latest recorded is June 17.  NRWS breeds in all 23 counties of
Maryland.

Hope this helps!

Norm

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Norm Saunders
Cambridge & West Ocean City, MD