In Kenn Kaufman's  "Lives of American Birds," the segment on Great 
Horned Owl contains the following sentence:  "May take over newly 
built hawk nest."

Seems like that is indeed what Bonnie Ott observed.

A couple of years ago, a pair of Downy Woodpeckers spent three busy 
weeks excavating a cavity in a rotten limb of one of our backyard 
maple trees.  As soon as they had finished, the hole was expropriated 
by Starlings.  Easier than doing it yourself, I guess.

Mike Bowen
Bethesda

D.H. Michael Bowen
8609 Ewing Drive
Bethesda, MD  20817
e-mail:  dhmbowenATyahooDOTcom