Adult white-naped cranes in Mongolia have unique color bands that identify them individually. Photo courtesy of the Wildlife Science and Conservation Center (WSCC) of Mongolia.
Understanding how animals use their environment to survive and thrive is a key challenge in predicting how global climate change will affect wildlife. A global collaborative study of four crane species reveals how migration is finely tuned to an unpredictable and complex environment.
Teams from 10 countries combined cutting-edge animal tracking technology, remote sensing information about the environment and new statistical frameworks to gain insights into four iconic species: the common crane, white-naped crane, black-necked crane and grey-crowned crane.
The study, led by scientists at the Max Planck Institute for Animal Behavior and Yale University, was published September 23 in the Proceedings of the National Academy of Sciences.
Researchers tracked the movements of 104 cranes across Africa, Asia and Europe using small GPS tracking devices, including unique solar-powered GPS leg bands developed by MPI-AB scientists. The tracking data revealed the impressive migrations the cranes undertook.
Some of their migration routes are more than 6,400 km round trip, requiring them to cross barriers such as the Alps, the Himalayas, the Arabian desert and the Mediterranean Sea.
In addition to their tracking studies, the researchers also developed a statistical framework to reveal how crane movements relate to aspects of the environment, such as the presence of nearby crops or water bodies, land temperature and vegetation cover.
“Animals have to satisfy their needs with what they get from their environment, and both are constantly changing,” said Scott Janko, lead author of the study and a postdoctoral researcher at the University of Michigan.
“This creates an interesting optimization problem, and we wanted to know whether cranes are solving it throughout their long-distance migration.”
The researchers found that all four crane species experience very different environmental conditions over the course of a year, and that these periods synchronized with key events in the cranes’ lives. This was particularly evident when comparing temperatures and resource availability in wintering and summer breeding grounds.
For some birds, the migration itself involved major changes in environmental conditions: Demoiselle Cranes, for example, crossed the Tibetan Plateau but had to contend with large fluctuations in temperature as they did so.
“We think this all has to do with different biological needs at different times of the year,” adds Janko, who conducted the study while at Yale’s Center for Biodiversity and Global Change. For example, cranes appear to intensify their visits to farmland in late summer, which coincides with the time they are raising their young and preparing for their autumn migration.
“This is exactly the time they’re going to want easy access to food,” he said.
For other species, access to food may come at a cost: the black-necked cranes studied had to choose between safe roosting habitat and abundant resources.
“Surprisingly, the balance of these competing needs shifted throughout the year depending on the birds’ behavior,” Janko adds: during migration, birds tend to choose safer roosting conditions, and during breeding season, they tend to seek out abundant food.
“We expected these shifts in focus depending on what the cranes need at any given time,” says Ivan Pokrovsky, a postdoctoral researcher at MPI-AB and last author of the study.
“But we were amazed at how the cranes cleverly used movement to resolve trade-offs between competing needs and access specific environments at key times of the year.”
Understanding how animals interact with their environments not only provides greater insight into how they survive in complex environments, but is also crucial for designing policies and management actions to address the twin threats of climate change and biodiversity loss, the authors say.
This research framework provides a statistical tool for understanding the complex relationships between animals and their environments and has broad applications in wildlife conservation and management efforts.
“By understanding how animals exploit specific environmental conditions, we can better predict how species will respond to human-induced global change and develop more effective interventions to ensure that the conditions they need to survive are maintained,” Pokrovsky said.
More information: Scott W. Yanco et al., “Migratory birds adjust niche trade-offs across seasons and life histories,” Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2316827121
Courtesy of the Max Planck Society
Citation: Study of four crane species reveals complex relationships between birds and their environment (September 23, 2024) Retrieved September 23, 2024 from https://phys.org/news/2024-09-crane-species-reveals-complicated-relationships.html
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