As birds breed earlier, nests end up in the path of farm equipment

By Dana Kobilinsky

An adult curlew stands on its breeding grounds. Earlier sowing times are destroying the birds’ nests on farms. Image courtesy of Aleksi Lehikoinen.

Birds that nest in farmers’ fields may find themselves increasingly in the path of farming equipment as climate change prompts the birds to breed before planting season begins.

Looking at farms in Finland, researchers found earlier springs have led farmers to move up their planting time, but birds are responding even faster, breeding before the fields have been sown. When birds lay eggs on fields that haven’t been sown yet, researchers found, farming activity can be fatal to their nests.

“It’s not very well known how humans are responding to climate change,” said Aleksi Lehikoinen, an academic research fellow at the Finnish Museum of Natural History and the University of Helsinki and coauthor of the study. “Species are doing it in various ways through phenological changes.”

The research can be applied globally, he said, and all farmers can consider making changes to benefit bird species that may use their land as habitat.

In the study published in Biological Conservation, the researchers studied the nesting time of lapwings (Vanellus vanellus) and curlews (Numenius arquata). They found the locations of newly hatched lapwing and curlew chicks, and based on known incubation period of the two species, were able to determine the average timing when they laid their eggs.

The team then collected data on sowing dates from the Natural Resource Institute of Finland, which keeps long-term datasets on when farmers started their sowing over the past few decades. “We calculated the trends for how much these activities have advanced and are influenced by variation in temperature,” he said.

The researchers found that on average, farmers have advanced their sowing dates by about one week in the last 38 years. Birds, on the other hand, have advanced their timing of breeding by two to three weeks.

This, Lehikoinen said, leads to situations where curlews and lapwings lay eggs on unsown fields that are likely to be run over by farming machinery.

Finnish curlew populations have declined by 20 percent in the last 30 years, Lehikoinen said, and they are also classified as vulnerable in Europe.

It’s not clear why farmers are responding so much slower to the warming climate than birds, he said, but it may be because the ground needs to be dry enough to plant.

Approaches to address the issue range from bottom-up techniques, such as locating and avoiding nests before planting and leaving aside portions of the land for nesting, to wider incentive-based strategies, including recent European Union agri-environmental measures to stop biodiversity loss on farms. “I think both are important,” Lehikoinen said.

Dana KobilinskyDana Kobilinsky is a science writer at The Wildlife Society. Contact her at dkobilinsky@wildlife.org with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.

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