Ian, a couple of years ago there was a Snowy Owl perched on the rooftops of 
several houses in the Cider Mill development in South Burlington. It was there 
for 3-4 weeks if I recall correctly. I am not sure if it was a 1st year female or 
male.
This location is pretty close to the corner of Barstow and Spear streets where 
you saw the Snowy Owl. I wonder if it is the same bird as these owls have very 
good longevity and the proximity of the these two locations raises the 
possibility that it is not a coincidence.
I will monitor the Cider Mill in the next few days to see if the bird visits that 
location.
Here is a photo of the Snowy Owl from Jan 2009:

http://www.flickr.com/photos/febco1/3225300671/in/set-72157623412718513

Ian, could you tell if the Snowy that you saw was a male of female? Thanks.

Fernando B. Corrada
South Burlington