YSM Issue 94.2

Ecology
FEATURE
that the ADCY8 gene had a large effect in
directing migration of peregrine falcons.
An epigenetic modification actually
results in over-expression of the ADCY8
gene in falcons that must travel long
distances, leading the research team to
believe that the gene is directly related
to long-term memory. This indicates
that migration is a combination of
intrinsic ability to remember pathways
and learned behavior from other falcons
or previous experience. This is also
supported by the fact that the level of
expression of the ADCY8 gene correlates
with the length of the migratory journey.
Yanco thinks this kind of research
touches on a question that has been everpresent
in the field of migration. “What
they've been able to do here,” he said,
“that is relatively new and I think very
few authors are working on, is the sort of
ultimate drivers. Why do it? How does it
happen? How does something like this
emerge in the first place in deep
evolutionary time? How is it
maintained?” These questions
will propel the field forward to
looking at the underlying why in
migratory patterns.
The research team then set
out to determine the history
of migration and how it was
impacted by large scale climate
changes in history, such as the melting
of the ice caps. By modelling historical
migration paths, they were able to
determine that as the ice caps melted,
northern falcon populations decreased
due to disruptions to their breeding
grounds. Breeding grounds shifted north
in order to maintain a similar temperature
environment for the falcons, lengthening
the falcons’ migratory path. As discussed
above, the length that a falcon can
travel is at least partially genetically
determined, meaning that only birds that
were genetically predisposed to remember
and travel long distances were likely to
survive long journeys. This particularly
brutal bout of natural selection resulted
in a dramatic decrease in the population
of peregrine falcons.
In addition to impacting the duration
of the migratory journey, changing
temperatures and melting glaciers also
impacted the directional orientation
of migration routes. During the last
Ice Age, or the Last Glacial Maximum,
there were many more accessible
wintering locations to the west, whereas
now, there are a relatively equal number
of western and eastern locations.
Both of these changes demonstrate
that global climate can have a marked
impact on migratory routes and relative
survival of the peregrine falcon species,
and likely other species of Arctic birds as
well. The findings offer a grave perspective
on the impact of current rising global
temperatures on Arctic avian populations.
Having studied how climate change has
impacted migration in the past, as well
as migratory routes in the present, the
research team then directed their attention
towards the future. To study how presentday
climate change would impact future
survival of the peregrine falcon species,
“Some groups of peregrine falcons
”
could lose between ninety and one
hundred percent of all suitable
breeding grounds.
they used ecological niche modelling
simulations to predict how rising global
temperatures would affect potential
breeding grounds and wintering areas.
The results were striking. Some
groups of peregrine falcons could lose
between ninety and one hundred percent
of all suitable breeding grounds, a
development that would be devastating
to those populations. As a result,
populations with short migratory routes
would see a decrease in migration
distance, eventually reaching the point
where they wouldn’t migrate at all,
while populations with long migratory
journeys would see further increases in
distance. Longer migration routes are
more closely correlated with mortality,
so lengthening an already long and
harrowing journey could devastate the
population size substantially.
IMAGE COURTESY OF WBUR
Melting ice caps in the Arctic reflect rising
temperatures and changes to Arctic climates that
threaten the breeding grounds and migration
routes of peregrine falcons.
According to data from the team, these
shifts have already begun. Retroactive
analysis of peregrine populations
found that population numbers have
been declining for the past twenty-five
generations: the future doesn't look
bright for peregrines.
What does this mean for the rest of us?
While some might hesitate to
understand how a peregrine falcon
can represent the world, this work
has done nothing if not convey how
interconnected our planet is. The
same climate changes that impact
these falcons will undoubtedly
have similarly intricate impacts
on our ways of life, especially if
no steps are taken to slow rising
temperatures in the coming years.
The Chinese team’s study is unique in
that it focused heavily on one species,
using a wide variety of tools and research
methods to create a complete and almost
definitive picture of the migration
patterns of peregrine falcons.
“One of the cool things in this study
was that they integrated approaches
that are often quite siloed. And I think
that this makes a compelling case
for putting together teams that can
do that stuff—that you're looking at
things behaviorally, environmentally,
ecologically, and [with] molecular tools,”
Yanco said. “I mean, I think there’s a
broad trend in science, that it’s becoming
more interdisciplinary and [with] larger
teams. As we reach the limits of what we
can infer with any given tool, it becomes
important to start expanding out.” ■
Gu, Z., Pan, S., Lin, Z., Hu, L., Dai, X., Chang, J., ... & Zhan, X. (2021). Climate-driven flyway changes and memory-based long-distance
migration. Nature, 591(7849), 259-264.
www.yalescientific.org
May 2021 Yale Scientific Magazine 33