A recent study published in the journal Proceedings of the National Academy of Sciences (PNAS) warns that the warming climate caused by climate change is poised to have a detrimental impact on bird populations, with an estimated 12 per cent decrease in the average songbird species. Researchers have found that the warmer climate will disrupt the breeding patterns of birds, leading to fewer chicks being produced.
The study, conducted by scientists from the University of California Los Angeles (UCLA) and Michigan State University in the United States, highlights that the mismatch between an early spring onset and the birds' readiness to breed is expected to worsen as global temperatures continue to rise.
The research reveals that birds experience reduced breeding productivity when they initiate breeding either too early or too late in the season. This phenomenon contributes to the projected 12% decline in the average songbird species.
"By the end of the 21st century, spring is likely to arrive about 25 days earlier, with birds breeding only about 6.75 days earlier," said the study's first author, Casey Youngflesh, currently a postdoctoral fellow at Michigan State.
For birds, timing matters when it comes to raising their offspring. The harsh weather while breeding too early or late could harm their eggs or newborns. What also matters is timing regarding food sources — looking for food before or after they're naturally available could mean the birds do not have the resources to keep their young alive.
In this 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, using data from a large-scale collaborative bird banding program.
Then, using satellite imaging, they determined when vegetation emerged around each site.
They found that the majority of birds were adversely affected by variations in the start of spring, even as some non-migratory bird species — the northern cardinal, Bewick's wren and wrentit among them — were found countering the trend.
However, the scientists said they were exceptions to the rule, because most non-migratory species couldn't keep up with earlier spring onsets.
For migratory species, earlier spring onset conditions meant even shorter breeding timeframes as after arriving at their breeding sites, birds need time to establish territories and prepare physiologically for egg-laying and offspring-rearing, before they start breeding.
The authors stressed that conservation strategies should address bird species' responses to climate-driven shifts.
"North America has lost nearly a third of its bird populations since the 1970s," said Morgan Tingley, a UCLA associate professor of ecology and evolutionary biology and the study's senior author.
"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," said Tingley.
