To survive warming, state birds nest earlier
The early bird not only gets the worm, but may stand a better chance of riding out global warming.
A new study finds that birds in California are breeding up to 12 days earlier than they did a century ago, an apparent effort to maintain their optimal nesting temperatures as the planet warms.
Like many plants and animals, birds have been known to relocate to cooler places to compensate for rising temperatures, moving north or to higher elevations. But the research published this month in the journal Proceedings of the National Academy of Sciences highlights the extent to which birds are going to adapt in other ways to a changing world.
“We hadn’t been thinking along those lines,” said Steven Beissinger, professor of conservation biology at UC Berkeley and a co-author of the study. “We always thought species would adjust where they are to stay in their thermal environment, not adjust their (reproductive) timing.”
He added, “The good news is that there may be more flexibility for species to respond to climate change than
we thought.”
The question for Beissinger and other researchers is whether such adaptations will save birds, and perhaps plants and other animals, as the planet continues to warm. Many forms of life, from polar bears to butterflies to sea coral, are already struggling with the 1.7-degree temperature rise since 1880, and models suggest the mercury will climb another 3.6 degrees by 2100. Some scientists are predicting a mass extinction.
Beissinger’s study of 202 species of California birds found that by nesting five to 12 days earlier in the year, birds are breeding at the same temperatures they did 75 to 100 years ago. Although other researchers have noted earlier nesting times, they theorized that birds were making the changes to when food was available — and that with spring coming earlier, insects and seeds were in greater supply earlier.
Bessinger’s study concludes that birds are moving up their nesting schedules to time the births of chicks with the temperatures they need to survive.
The researchers arrived at their conclusions by trekking across California over the past seven years to record bird behavior from Lassen National Park in the north to Los Angeles. Then they compared their observations with bird surveys made by the pioneering UC Berkeley biologist Joseph Grinnell from 1911 to 1929.
The team discovered that, over the past century, about half the bird populations had moved north or to higher ground in response to warmer weather. Many of the others were nesting earlier.
The researchers, who also included scientists from the University of Connecticut and the U.S. Agency for International Development, said there may be limits to how much earlier birds can nest. As temperatures continue to climb, the window for nesting is likely to get shorter, which will reduce birds’ ability to breed a second time if a first attempt fails. Also, larger birds with longer nesting periods may simply run out of time to reproduce.
“We don’t know yet whether staying in place and shifting schedules earlier is a permanent solution or only provides temporary relief,” Beissinger said.
Another study by researchers at UC Davis, published this week in the journal Ecology Letters, underscores the importance of an animal’s neighbors in its ability to withstand climate change.
The researchers found that many forms of marine life in
the rocky intertidal zones along the West Coast, from crabs to abalone to small fish, rely on the shade and moisture of mussel beds, seaweed and algae to stay cool, especially at low tide.
“There’s not many marine animals that could survive being thrown up on the blacktop for six hours a day,” said the lead author Laura Jurgens, who was a doctoral candidate at the UC Davis Bodega Marine Laboratory when the study was done. “If you’re an octopus living in a mussel bed, the most important thing to keep your body temperature survivable is that mussel bed around you, not whether you live in Southern California, where it’s warmer, or Washington.”
Erik Beever, a U.S. Geological Survey research ecologist who focuses on climate adaptation and was not part of the either new study, said a number of factors are making it possible for plants and animals to withstand global warming, and researchers are gaining a better understanding of these adjustments.
The success stories, he said, usually come from more mobile forms of life, such as birds, or ones with hardier constitutions, such as coyotes and cockroaches. Some creatures even make physical changes to adapt.
For example, researchers have found that banded snails in Europe are evolving toward lighter, cooler shells, and some Alaskan salmon have undergone genetic changes that prompt them to migrate through rivers earlier to account for warmer water.
Many plants and animals, however, can’t adapt, Beever said. Others have their limits.
“In some sense, if we say, ‘Oh yeah, no problem, animals will be able to compensate for this,’ it may give us a false sense of hope,” Beever said.