Brainy birds may fare better under climate change
Study is first to directly link cognitive power to a physical response to warming

Date:
February 10, 2022
Source:
Washington University in St. Louis
Summary:
Many North American migratory birds are shrinking in size as
temperatures have warmed over the past 40 years. But those with
very big brains, relative to their body size, did not shrink as
much as smaller-brained birds, according to new research. The
study is the first to identify a direct link between cognition
and animal response to human-made climate change.



FULL STORY ==========================================================================
Many North American migratory birds are shrinking in size as temperatures
have warmed over the past 40 years. But those with very big brains,
relative to their body size, did not shrink as much as smaller-brained
birds, according to new research from Washington University in
St. Louis. The study is the first to identify a direct link between
cognition and animal response to human-made climate change.


==========================================================================
The body size changes in songbirds are small but significant, affecting familiar species of sparrows, warblers and thrushes. In fact, the
size changes are so pervasive that some scientists have suggested
that reductions are a universal response to warming. But new research
published in Ecology Letters shows that bigger-brained birds have been
able to out-think shrink, at least to a certain extent.

"As temperatures warm, body sizes are decreasing," said Justin Baldwin,
a PhD candidate in the laboratory of Carlos Botero, assistant professor of biology in Arts & Sciences at Washington University. "But larger-brained species are declining less strongly than small-brained species."
Baldwin and his co-authors analyzed information on some 70,000 birds
that died when they collided with buildings in Chicago from 1978 to
2016. They augmented this vast dataset, first published by researchers
at the University of Michigan, with new brain volume measurements and
lifespan data for 49 of the 52 species of North American migratory birds included in the original study.

Birds that had very big brains, relative to their bodies, had body size reductions that were only about one-third of those observed for birds
with smaller brains, the Washington University scientists discovered.

And bigger brains matter for birds.



========================================================================== Relative brain size is often considered a proxy for behavioral flexibility
in birds. The idea is controversial when it is applied to some other
animals, Baldwin said, but it works well for birds.

"Relative brain size correlates with increased learning ability,
increased memory, longer lifespans and more stable population dynamics," Baldwin said.

"In this case, a bigger-brained species of bird might be able to reduce
its exposure to warming temperatures by seeking out microhabitats with
cooler temperatures, for example," he said.

The new findings are significant because this is the first time scientists
have been able to show a direct link between cognition and phenotypic
responses to climate change.

More or better options It's not entirely clear why so many songbirds
are shrinking in size as temperatures rise. One possible explanation
is that heat causes stress, and birds with smaller bodies can dissipate
heat better. This explanation is consistent with observations that birds
that live in the warmer parts of their species' normal geographic ranges
are smaller than those that live in the colder parts of their range.



==========================================================================
But downsizing comes at a potential fitness cost -- e.g., increased
predation or reduced competitive ability -- that birds in general may want
to avoid. In that context, having a larger brain may offer alternatives
that are not available to small-brained species.

"One of the first things that jumps out to me from these findings is
that we can already see that climate change is having a disproportionate
effect on species that have less capacity to deal with environmental
change through their behavior," Botero said.

"This doesn't mean that climate change is not affecting brainy birds,"
Botero said, "or that brainy birds are going to do just fine. What our
findings suggest is that climate change can have a much stronger effect on
the less- brainy birds." "The species we studied only spanned a two-fold difference in relative brain size, which was enough to reduce the effects
of increases in breeding temperature by 70 percent," Baldwin said. "This
tells us that even small differences in cognition matter." The findings
also have practical implications for conservation, as 3 billion birds
(about one in three) have been lost in North America since the 1970s.

"That's probably a lot of natural selection that hits different species differently," Baldwin said.

"Rapid changes in the environment often produce a few winners and
a whole lot of losers, which is really unfortunate," he said. "Many
wildlife populations have moved toward colder places as the planet has
warmed. Selection forces those that don't move to adapt, for example,
by changing their body size.

Baldwin's analysis reveals that smaller-brained species might be under especially strong natural selection, a fact that planners may need to
take into account for conservation management.

"When it comes to climate change mitigation and planning, a major goal
is to maintain population-level connectivity," Baldwin said. "We want
to allow species to move toward the poles or upslope in elevation, to
keep up with warming climates. Our findings suggest that this type of intervention could be especially important for smaller-brained species." ========================================================================== Story Source: Materials provided by
Washington_University_in_St._Louis. Original written by Talia
Ogliore. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Justin W. Baldwin, Joan Garcia‐Porta, Carlos
A. Botero. Phenotypic
responses to climate change are significantly dampened
in big‐brained birds. Ecology Letters, 2022; DOI:
10.1111/ele.13971 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220210084942.htm

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