[CT Birds] mockingbird follow-up

Chris Elphick elphick at sbcglobal.net
Wed Mar 28 07:42:12 EDT 2012


Carol asked about reasons for the changing mockingbird numbers.  I have not done 
a careful search of the literature, but the general dogma is that the initial 
increase was due to a combination of suburbanization (which brings in 
berry-producing shrubs and may have other advantages for birds that will settle 
there - e.g., reduced nest predation rates), a warming climate that has allowed 
northward expansion of numerous species, and the spread of the invasive 
multiflora rose.  I think there is at least one study that makes a strong case 
for the importance of the latter, but don't recall the details.

I've not seen anyone address the more recent decline, but my hypothesis would be 
that it is likely related to the loss of early successional habitat - open 
fields with scattered bushes are increasingly turning into young forest or 
(probably more likely, especially in more recent times) being developed.  One 
way to test these ideas would be to look back at habitat change in the vicinity 
of BBS points and see if changes occur where/when numbers decline.

If others shared Roy's question about the "1966" date, it simply indicates that 
the gray line represents the population level in 1966 when the survey began.  
The slow load and lack of explanation on the graph itself are things that will 
be fixed once the web site is completed.

Chris

 Chris Elphick
Storrs, CT
elphick at sbcglobal.net



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