Bird numbers decline in early spring due to warming climate, study finds

A warming climate is causing birds to produce fewer offspring by bringing spring weather forward, so the birds’ breeding season and birds are less ready to breed, according to new research.

Research suggesting that reproductive productivity could decline by about 12 percent for the average songbird species suggests that the mismatch between early spring and bird breeding will worsen as the world warms.

Birds produce fewer babies if they start breeding early or late in the season, research led by scientists from the University of California Los Angeles (UCLA) and Michigan State University in the US has found.

The researchers reported in their study that as a result of climate change, the birds were unable to keep pace due to weather similar to the previous spring.

„By the end of the 21st century, spring may arrive 25 days earlier, and birds will breed 6.75 days earlier,” said Casey Youngflesh, the study’s first author and now a postdoctoral fellow at Michigan State.

For birds, time is of the essence when raising their offspring. Severe weather during early or late breeding can harm their eggs or newborns.

Timing of food sources is also important – foraging for food before and after they are naturally available means birds do not have the resources to keep their young alive.

In this study, researchers calculated the timing of breeding and number of chicks for 41 migratory and resident bird species at 179 sites near forests across North America between 2001 and 2018 using data from the Large-Scale Collaborative Bird Banding Project.

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Then, using satellite imaging, they determined when vegetation emerged around each site.

The scientists, collectively, found that the species bred a day earlier, with leaves appearing on the trees every four days earlier, marking the start of spring.

They found that most birds were badly affected by the early spring changes, with some migratory bird species – including the northern cardinal, Bewick’s wren and the wren – bucking the trend.

However, scientists say they are exceptions to the rule, as most migratory species can’t keep up with earlier spring starts.

Migratory species are short-lived breeders, as they need time to establish their territories and physiologically prepare for spawning and rearing of offspring before they begin breeding after the early spring stages arrive at their breeding sites.

The authors emphasized that conservation strategies should address the responses of bird species to climate-driven changes.

„North America has lost nearly a third of its bird population since the 1970s,” said Morgan Dingley, associate professor of ecology and evolutionary biology at UCLA and senior author of the study.

„While our study demonstrates that the worst impacts of the timing mismatch may not occur for decades, we need to focus now on concrete strategies to increase bird populations before climate change takes its toll,” Dingley said.

(This story was not edited by DevDiscourse staff and was generated automatically from a syndicated feed.)

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