Text of a notice in today's science section of the Times:

A Chickadee Mating Zone Surges North   (NY Times pg D-2, 3/18/2014)
        In a long, narrow strip of territory from Kansas to New Jersey, two
closely related species of chickadees meet, mate, and give birth to
hybrid birds. Now scientists are reporting that this so-called hybrid
zone is moving north at a rate that matches the warming trend in winter
temperatures.
        "It has moved north by about seven miles in the last 10 years," said
Scott Taylor, an evolutionary biologist at the Cornell Lab of
Ornithology at Cornell University.
        The northward movement of the strip "corresponds closely to warming
global temperatures," Dr. Taylor said. "The fact that these little birds
are experiencing this makes it really relatable." (The species are the
Carolina chickadee, from the South, and the black-capped chickadee, from
the North.
        The scientists, who reported their findings in the journal
Current Biology, relied on blood samples drawn from chickadees in
Pennsylvania from 2000 to 2002 and from 2010 to 2012, and on sightings
of hybrid chickadees recorded in the citizen science database eBird.
They found that hybrids were sighted in areas where the average
temperature in winter was 15 to 19 degrees Fahrenheit (minus-9 to
minus-7 Celsius)--the same readings as a decade earlier, but in a zone
seven miles north of the 2000-02 sightings.
        The adaptability of the chickadees is impressive, Dr. Taylor said, but
less mobile organisms that cannot move as fast may be suffering.
        For these organisms--like small mammals, insects, and plants--the
warming temperatures could have serious implications that are not
immediately apparent, he said.     SINDYA. N. BANHOO

                         *   *   *   *   *

        This is another study confirming what birders have noticed in Ohio for
generations. Here in the center of the state, Wheaton in 1882 wrote that
the Carolina chickadee did not winter this far north at the time, only
the black-capped. By 1903 Lynds Jones wrote that Carolinas still did not
breed north of Columbus.  In 1924 E.S. Thomas wrote he had never seen a
black-capped chickadee in Columbus--all chickadees throughout the year
were Carolinas, but he was later to witness incursions of black-caps in
Columbus, with one way down in Hocking County in 1957. In 1961, it was
still called "plentiful in town by December" (American Birds 16(1):41),
and Trautman had been counting 50+ black-caps a day in November.  Their
numbers retreated into small ones by the '80s, and in recent decades
they have been mostly absent, with only a handful of reports, always in
winter. Overall, the rate of movement posited by Dr. Taylor seems to
match our experience with other species.
        During those decades the reliable black-capped range has been
retreating north, with the "chickadee line" advancing from here to
Killdeer Plains to Rte 30, and now folks in Wooster remark on the
growing number of chickadee hybrids. The frontier is moving
north--though maybe not at the measured pace the Cornell NY Times
article suggests--but overall steadily. Folks in Pennsylvania have
noticed the same thing, and they have done a lot more careful work.
        It is significant that the changes in bird distribution over the past
150 years, well verified as it was for most of that time by museum
specimens, shows this. There are lots of Ohio breeding species once
regarded as "southern birds"---mockingbird, black vulture, egrets, barn
owl, titmouse, w-b nuthatch, red-bellied woodpecker, etc--that have
expanded their ranges into and beyond Ohio in good numbers.
        I had to smile at the inclusion of data from eBird in the description
of the article--which I have not read this, but plan to seek at the
University library. In other forums like ours, a number of folks around
the country have questioned how reliable eBird data might be in
comparison to the blood samples in this study. I know this is a pet
project of Cornell's, and relentlessly publicized, but no scientist is
going to trust the IDs of chickadees--including hybrids and
back-crosses!--reported by random eBirders of varying abilities in such
a study. Even if all those reporters happened to be correct in their
field identifications, eBird lacks, and seems to ignore, historical
records, so is doubly inadequate to the task.
        A question for the shrinking number of global-warming skeptics:
over the sliver of time for which we have records, the ranges of
southern bird species seem to be expanding north. Can you think of any
northern species making inroads on a similar scale in the south?  The
only example that occurs to me is the bobolink...
Bill Whan
Columbus


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