I asked a few days ago if anyone had noticed declines in numbers of
house wrens in the state this spring, and have just returned from three
days of atlasing birds. I find I got 59 answers, from at least 26
counties, all from folks who notice such things.
     I promised to summarize what I heard, and here is an attempt to do
so without getting overly concerned with anecdotal evidence. First of
all, just asking if anyone has noticed a decline in house wrens probably
biased the results, as more folks who've noticed missing birds will
answer than those who have not. Many samples--for instance back-yard
observations--are much less significant than wider surveys; one's pair
of house wrens will not live forever, after all. Respondents with years
and years of records understandably have more information than those who
don't. Also, I failed to ask folks to separate reports of migrant birds
passing through vs. nesters; birds who've lost territory may
nevertheless pass through it in spring and fall. They are virtually
unknown in the winter season here, so their arrivals are easily noticed,
and nesting males are noisy and easy to detect.
     By a ratio of about 11 to 7 respondents reported fewer house wrens.
And a large proportion of the reporters who did more comprehensive
surveys--not just back yards, etc.--felt there were fewer. Only a few
respondents felt this species had actually increased in numbers. All in
all I'd say there seems to be some reason to pay more attention to the
numbers of house wrens, as there may be fewer nesters recently---and
this may be the only lesson learned here.
     House wrens have increased considerably in numbers here over the
past century. More rigorous studies, such as the Breeding Bird Atlases,
show they are somewhat less numerous as nesters in the southeasternnmost
part of the state (see
http://bird.atlasing.org/Atlas/OH/Main?cmd=stateSummary&theme=species&edition=current&species=houwre&species=Go
  also see http://www.nenature.com/HouseWrenBreedingMap.htm): it is
possible their lower population in Ohio's SE may have decreased
recently, according to reporters. Still, most references say their
population is on the rise overall; if there is a decline, it must be
quite recent. Still, some careful climate-change projections show
nesting house wrens will have moved entirely north of Ohio in the future.
        Even with all the helpful comments I received, I believe the question
is not settled. Answers to larger questions like this will most reliably
come from careful surveys such as those conducted by the Ohio Breeding
Bird Atlas, and if you have questions like this I recommend helping them
out while there's still time: http://www.ohiobirds.org/obba2/
Thanks to all who wrote,
Bill Whan
Columbus

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