Rising temperatures worldwide and the early arrival of spring due to climate change-driven shifts are having a strong effect on birds.
According to a new study led by scientists at UCLA and Michigan State University, birds cannot keep up with the earlier arrival of spring caused by climate change. As a result, they’re raising fewer young. The study, which was published recently in the Proceedings of the National Academy of Sciences, focused on North American songbirds.
The study also says that by the end of the 21st century, climate change will cause springlike weather to begin 25 days earlier, but birds will only breed about seven days earlier. According to a press release from UCLA, that change could lead to an average reduction of 12% in breeding productivity for songbird species.
As the release explains, the researchers used data from a large-scale collaborative bird banding program run by The Institute for Bird Populations, a California-based non-profit organization, for the study. The researchers calculated the timing of breeding and the number of young produced for 41 migratory and resident bird species at 179 sites near forested areas throughout North America between 2001 and 2018.
The authors of the study then utilised satellite imaging to determine when vegetation emerged around each site. “They found that each species had an optimal time to breed, and that the number of young produced decreased when spring arrived very early, or when breeding occurred early or late relative to when plants emerged,” the release adds.
“North America has lost nearly a third of its bird populations since the 1970s,” Tingley said. “While our study demonstrates that the worst impacts of timing mismatch likely won’t occur for several decades yet, we need to focus now on concrete strategies to boost bird populations before climate change takes its toll.”
The study found that while the majority of birds were adversely affected by variations in the start of spring, several species — including the northern cardinal, Bewick’s wren and wrentit among them — countered the trend, demonstrating improved breeding productivity when spring began earlier. These species, as the UCLA release explains, are mostly non-migratory species that can respond more quickly to the emergence of spring plants that signal the start of the breeding season.
"But those species were the exceptions to the rule. Even most non-migratory species couldn’t keep up with earlier spring arrivals. Overall, for every four days earlier that leaves appeared on trees, species bred only about one day earlier... For migratory species, that discrepancy means that the time between when they arrive at their breeding sites and breeding itself is likely to get shorter as springlike conditions begin earlier," the release adds.
The authors and researchers of the study noted that it is critical that conservation strategies should address avian responses to climate-driven shifts. “North America has lost nearly a third of its bird populations since the 1970s,” Morgan Tingley, a UCLA associate professor of ecology and evolutionary biology and the study’s senior author said in the press release. “While our study demonstrates that the worst impacts of timing mismatch likely won’t occur for several decades yet, we need to focus now on concrete strategies to boost bird populations before climate change takes its toll.”
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