The grapevine tells me that the AOU checklist committee has voted to split Pacific Wren from Winter Wren. This is fourth-hand information, but it originates with a member of the checklist committee and I believe it’s reliable.
This means the split is a done deal, but it’s not official until the committee publishes its 51st supplement to the checklist, which will happen in July 2010. Between now and then, it would behoove birders, especially those in the Mountain West, to pay very careful attention to any Winter/Pacific wrens they may encounter. Here in Colorado, we still have a lot of work to do to try to figure out the occurrence patterns of the two species, and I bet the same is true in many other states as well. Although there are certainly visual differences, sounds remain a key distinction between these species; see my earlier posts on differentiating them by call and by song.
Meanwhile, if you’re looking for more information on why these two species are being split, check out Nick Sly’s post on the subject from 2008. It’s marvelous.