[cobirds] Re: House Wrens increasing in Denver

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 

On Tuesday, July 14, 2015 at 4:42:08 PM UTC-6, Robert Righter wrote:

Hi all

The House Wren has always been an infrequent spring and fall migrant in our neighborhood in Denver. Last summer a few House Wrens were noted in our backyard. This summer the House Wren has blanketed not only our backyard but the whole neighborhood's backyards, to where the wren the now is the most common breeding bird species.

It is curious what environmental factors have triggered this increase. We rightfully take note of birds decreasing in populations but rarely take note of bird population increasing, except those that are considered pest species.

Could there could be common environmental reasons  for populations both increasing and decreasing? Perhaps knowing the reasons why some birds are increasing could help explain why some birds are decreasing? 

Bob Righter

Denver CO 

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