(CN) – Shortly before pioneering ornithologist Eberhard Gwinner died, he replicated one of his studies that showed climate change affects a bird’s internal migration clock.
Gwinner would not be able to see the results of his last study, but nearly 20 years later those results are now published in the scientific journal Current Biology.
His colleague Barbara Helm participated in the 2002 study where the research team sought to discover how much impact climate change has on the pied flycatcher’s circannual clock, but with the lead researcher gone, the data went unpublished.
Now an associate professor at the University of Groningen in the Netherlands, Helm published the results of that experiment Thursday.
The findings show that climate change has offset the internal clocks of migrating birds, which are shedding their winter feathers and laying their eggs earlier in the year.
Gwinner, a German pioneer in the study of birds and their circannual clock, first conducted his study in 1981. He hand-raised newly hatched pied flycatchers and observed them in a laboratory for nearly a year. Through that experiment, Gwinner demonstrated the mechanisms of the bird’s internal clock that announces the start of migration.
The European pied flycatcher takes its cues from the environment. Birds kept in cages and shielded from the outdoors still became anxious around the end of their winter molting and the growth of their reproductive organs as spring approached, according to the study.
Helm said the 2002 experiment included many of the original measurement devices and cages, along with modern ones.
“It was quite unique to have both the original setup and the raw data from the first experiment,” Helm said.
Gwinner’s lab was dismantled after his death in 2004, which meant the experiment could not be replicated under the same conditions. And the analysis of the data was delayed by several years as Helm went on to work on other projects.
In 2018, Helm was appointed at the University of Groningen, allowing her to finally write the paper on the 2002 experiment.
The study results showed that the birds were thrown for a loop by the approach of spring. Their internal clocks were advanced by 9.3 days and growth of their reproductive organs, which emerge as the weather heats up, also occurred earlier. Meanwhile, changes from autumn migration were slightly delayed.
The results confirmed the initial theories on climate change and how it affects a birds’ migration patterns, but what about birds in the wild?
Researchers were fortunate to find a couple of hobby scientists – Dieter and Ute Hoffmann – who had been observing and recording the behaviors of birds near their home for nearly 50 years.
This allowed researchers to compare their data to the previous experiment and data from birds in the wild. The Hoffmans are listed as co-authors in the paper, along with doctoral student Benjamin Van Doren from the University of Oxford who related the datasets in the experiment.
Birds in the wild were found to lay their eggs 11 days earlier than usual, illustrating some form of observable evolution.
“The good news is that there is more adaptive potential than we previously thought,” Helm said.
The lingering question is how elastic these birds can become when change interferes with their feeding habits as they return to Africa from Europe earlier in the year and find less caterpillars and more birds competing for food.
Helm adds it’s impossible to pursue more answers with this particular experiment model.
“When the Gwinner lab was closed, all the original equipment was discarded, so it's now impossible to truly replicate the study,” Helm said.