As the climate changes, species are shifting across the surface of our planet. Migration patterns are changing, breeding seasons are beginning earlier and animals are moving northward. With all of this happening, you’d think that birds would be drastically affected in a negative way. Yet new research has shown that, surprisingly, songbird populations can handle far more disrupting climate change than expected.
Spring may have started late this year, but the general trend shows an earlier spring for the last four decades. Because of this earlier spring, the seasonal timing of trees and insects also advances. Yet while trees and insects advance, songbird species such as the Parus major, also known as the great tit, lag behind.
In order to see how these seasonal changes affect songbird populations, researchers examined the great tit populations using almost 40 years of data from the songbird. More specifically, they looked at the great tit population in the Dutch National Park.
Their findings, unfortunately, didn’t seem to bode well for the birds at first. “It’s a real paradox,” said Tom Reed and Marcel Visser of the Netherlands Institute of Ecology in a news release. “Due to the changing climate of the past decades, the egg laying dates of Parus major have become increasingly mismatched with the timing of the main food sources for its chicks: caterpillars.”
In fact, it turns out the seasonal timing of the food peak has advanced over twice as fast as that of the birds. This means that while the caterpillars are showing up earlier with the earlier spring, the birds haven’t quite caught up yet which, in turn, means less food for the chicks.
Despite this fact, though, population numbers don’t seem to be down that much. Upon further examination of the data, the researchers found out why. Although fewer offspring now fledge due to a food shortage, it turns out the ones that do fledge have a higher chance of survival until the next breeding season. This offsets the current feeding issue.
“We call this relaxed competition, as there are fewer fledglings to compete with,” said Reed in a news release. “It all seems so obvious once you’ve calculated this, but people were almost sure that mistiming would lead to a direct population decline.”
In fact, some of the songbirds are benefiting from the earlier springs. Some of the great tits that lay their eggs earlier in the spring are more successful than the ones that lay latter and which produce relatively few surviving offspring. This, in turn, leads to increasing selection for birds that reproduce early.
While numbers aren’t being affected yet, though, researchers estimate that they probably will be in the future. The mismatch between egg laying and caterpillar peak continues to grow, which means that the impact of the phenomenon will also increase. While birds may be able to compensate for now, the future may cause a drop in population numbers.