Bird populations are in rapid decline across North America.
While climate change is just one of the many factors influencing
North American birds, its effects are significant and can interact
with other stressors, such as habitat loss. A team of University of
California, Davis, researchers found that the effects of extreme
temperatures on avian reproduction can vary depending on the type
of environment that birds call home.
Researchers found that extreme high temperatures significantly
diminish bird reproductive success in agricultural landscapes.
Birds nesting near farmland were half as likely to have at least
one fledgling successfully leave the nest when temperatures spiked.
However, forests seemed to provide a protective buffer against high
temperatures, offering shaded areas that helped increase nesting success.
“The effects of heat are more intense for birds nesting in agriculture
than birds nesting in forest, which means that canopy cover probably
constitutes an important climate refuge for birds that can thrive in
various habitats,” said Katherine Lauck, co-lead author of the paper
and a Ph.D. candidate in ecology at UC Davis.
When they looked at how heat waves affected nesting success in urban
areas, the researchers found less of a negative impact than in agriculture,
probably because nests were often in city parks and residential areas
that can have high tree cover.
The researchers also studied which types of species were most vulnerable
to heat waves in agriculture. Negative impacts were broadly felt across
all bird species studied, with western bluebirds and tree swallows, two
species common on farms, both experiencing significant declines in
nesting success when temperatures spiked in agricultural areas.
“We see these strong effects in common and habitat generalist birds,
which we often think of as more resilient to land use change and climate
change,” Lauck explained.
Threatened birds and birds that build open-cup nests, which lack any
covering, were even more vulnerable to heat waves in farming areas
compared to common species and those that build their nests in tree
holes and nest boxes.
Future predictions and solutions
The study also painted a picture of what the future may look like. By
the year 2100, their models predicted that nesting success in agricultural
areas would decline by an additional 5% on average under current greenhouse
gas emission trajectories. The study suggests that curtailing emissions
and promoting thermal refuges, either by planting or maintaining patches
of natural vegetation, are likely crucial to conserving birds. Keeping
shade may also be needed to maintain bird populations living in urban
and agricultural areas.
“Farmers often build nest boxes to attract birds to their farms and
help control insect pests. Maybe it makes sense to put those boxes in
shaded locations,” Karp said. “They might also consider planting
hedgerows and conserving patches of native vegetation to provide shade
and help birds beat the heat. Thinking about some of those interventions
might matter a lot for birds looking forward.”
Provided by the IKCEST Disaster Risk Reduction Knowledge Service System