Just to add some available information to the HOWR issue:
House Wrens are usually the second most commonly caught species at our Chatfield banding station (after Yellow Warblers). We assume that the vast majority of those we catch are summer residents (rather than migrating through). What we've observed over the 12 years is that HOWR populations fluctuate. We've had 3 peaks - 2005, 2009 and 2015. (Not quite every 5 years, but close.) In the peak years, we caught twice as many (~80) as we did in the lowest years (<40). We hit our highest number this year at 83.
I wonder if some of the competition being observed this year is the result of the particularly high number of HOWRs this year, as part of a pattern of fluctuating numbers.
Meredith McBurney
Bander, Chatfield Station
Rocky Mountain Bird Observatory