November 13, 2017
A new study suggests that many of
the state's birds are adapting to rising temperatures by breeding earlier than
they did a century ago.
A comparison of nesting data
recorded in the early 1900s with similar data today for more than 200 species
of California birds shows that overall they are breeding five to 12 days
earlier than they did 75 to 100 years ago.
Earlier studies found that many
but not all birds in California's mountains are moving north or to higher elevations to
find cooler temperatures in the face of global warming.
"The shift to earlier
breeding that we detected allows birds to nest at similar temperatures as they
did a century ago, and helps explain why half the bird species in the
mountainous areas of California did not need to shift upward in elevation in
response to climate warming over the past century," said co-author Steven
Beissinger, a UC Berkeley professor of environmental sciences, policy and
management.
The study, led by former UC
Berkeley graduate student Morgan Tingley, now an assistant professor at the
University of Connecticut in Storrs, UConn postdoc Jacob Socolar, former UC
Berkeley postdoc Peter Epanchin, now of the United States Agency for
International Development, and Beissinger will be published online the week of
Nov. 13 by the journal Proceedings of the National Academy of Sciences.
Early spring arrivals have long
been noted by the public and reported by scientists, but the assumption has
been that the birds are tracking resources, primarily food: with warming
temperatures, plants produce leaves and seeds earlier, and insects emerge
earlier.
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