I was wondering if the cause was a Great Horned Owl, but wondered why one 
would be in Silver Spring near the Metro!  A peregrine makes better sense...

I work in downtown Silver Spring (by the Metro).  During winter I see a 
peregrine here almost daily, and if you wanted to actually look for one, they 
could probably be seen daily.  Hard to say where a good place to look from 
might be, but they rule the airspace of the tall buildings around the Metro.  I 
have seen both adults and juveniles here.  During migration they are only seen 
occasionally here, but interestingly they are often using the same habitat as 
the bird(s) that are here in winter.  They have been using this area in winter 
for at least 3-4 years, as far as I know, but only occupy the area as an 
overwinter habitat.  I have not ever seen them during breeding season, or I 
would have made a mention of it before.

CAUTION - I would not go wandering around the area looking up at the 
buildings with binoculars - you may attract the attention of police or building 
security guards.  It is an employment area with many federal agency 
employees, so there is no shortage of security eyes around here.

Now I'm curious... I will go and look under one of the favorite peregrine 
perches to see if there are any bird parts around.  It's hard to say where they 
could fall, since it is so high up, but I have seen them eating birds there often.

Cheers-
Jeff Shenot
Croom MD