Climate change threatens breeding birds
Birds risk starvation if they start breeding early due to climate change


Date:
September 28, 2020
Source:
Max-Planck-Gesellschaft
Summary:
Surviving on a warming planet can be a matter of timing -- but
simply shifting lifecycle stages to match the tempo of climate
change has hidden dangers for some animals, according to new
research. The study has uncovered drastic consequences for
birds that are breeding earlier in lockstep with earlier starts
of spring: chicks hatching earlier face increased risk of poor
weather conditions, food shortages and mortality.



FULL STORY ==========================================================================
The researchers, who examined decades of data on weather, food
availability and breeding in Tree Swallows, say that the timing of
when to breed and when food is available is becoming decoupled for some
animals -- highlighting the complexity behind how organisms respond to
climate change. "Simply moving dates earlier to track climate change isn't necessarily risk free. Riskier conditions earlier in the year can expose animals to unintended consequences when responding to bouts of unusually
warm spring weather," says Ryan Shipley, postdoctoral fellow at the Max
Planck Institute of Animal Behavior and first author on the paper.


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In recent years, studies have raised concerns about whether or not species
can adapt, or "keep pace" with climate change. Particular emphasis has
been placed on phenology -- the timing of life cycle events such as
breeding and migration -- and the importance of adjusting this to track
rising temperatures and earlier arrivals of spring. But the authors
say that breeding earlier may place animals at greater risk of exposure
to inclement weather events that tend to occur more frequently earlier
in the year. They found that Tree Swallows had been advancing breeding
by three days every decade for the last 30 years, but earlier-hatching offspring were at greater risk of exposure to inclement weather, which in
turn reduced the availability of the flying insects they rely on for food.

"Our results raise the possibility that animals relying on food
resources that can rapidly change in abundance due to the weather may
be particularly at risk to climate change," says Shipley. The study has
exposed strong fitness consequences for birds that are advancing breeding
at a similar rate to climate change. But it may also provide clues to
the mystery of why aerial insectivorous birds, such as swallows, swifts, flycatchers, and nightjars, are declining faster than other groups in
much of North America and Europe. Weather in spring can change quickly
and tends to be more unpredictable earlier in the year.

Changing climates The activity of flying insects is determined by weather, which means they are stochastically available. "For birds that feed on
flying insects, one day is feast, the next is famine. This means during unusually warm springs, parents are betting current conditions that
prompt earlier egg laying are indicative of similar good conditions for
rearing hatched young three weeks in the future," says Shipley.

The results lay bare a previously unobserved threat to aerial
insectivorous birds. "Considerable attention has been given to potential widespread decline of insect populations and this might be hitting insectivorous birds particularly hard. But we show a mechanism that
doesn't require change in insect abundance -- just availability over
short time, like a few days." The researchers studied a population
of Tree Swallows in Ithaca, New York, that have been the focus of a
remarkable 30-year experiment -- studies of this length are rare in the
field of ornithology. This allowed them to analyse a series of long-term
data of Tree Swallow reproduction (over 30 years) daily insect abundance
(over 25 years) and weather (over 100 years).

"Long-term studies like this one are vital for understanding how and why species are affected by changing climates. They can also provide valuable insights into how organisms function, interact in complex ecological
networks, and evolve," says Maren Vitousek, Associate Professor in the Department of Ecology and Evolutionary Biology at Cornell University, and co-author on the study, who runs the longterm Tree Swallow experimental
site in Ithaca.


========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. J. Ryan Shipley, Cornelia W. Twining, Conor C. Taff, Maren
N. Vitousek,
Andrea Flack, David W. Winkler. Birds advancing lay dates with
warming springs face greater risk of chick mortality. Proceedings
of the National Academy of Sciences, 2020; 202009864 DOI:
10.1073/pnas.2009864117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200928152909.htm

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