Interesting question. I can still hear two counter-singing Carolina Wrens by my
house near Frederick. I explored eBird data. Right enough, the "abundance"
measure for last week (beginning 3/15) was lower than in the same week in the
previous 3 years (0.34, compared to 0.50,0.47, 0.58 in 2007-09). However, the
"birds/hour metric" was higher than in 2007 and 2009 but lower than 2008. Quite
surprising. These data suggest there has been a decline, but it's not
disastrous - a level of mortality that could be compensated for in one very
productive breeding season. BBS counts from the upcoming spring should give us
a better handle on this though.

Andy Wilson
Frederick
photo galleries at: http://www.pbase.com/andywilson