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.