How do scientists follow an impressively long bird migration? They give a crane a GPS. A team of scientists used small GPS leg bands to follow 104 of these wading birds as they traveled across parts of Asia, Africa, and Europe. The tracking data revealed that some of their routes are more than 3,976 miles round trip, navigating several natural barriers along the way. They also saw that the cranes face several make-or-break decisions about where and when they stop. The findings are described in a study published September 23 in the journal Proceedings of the National Academy of Sciences (PNAS).
“Animals have to satisfy their own needs with what they can get from their environment, but both of these are changing constantly,” study co-author and University of Michigan postdoctoral researcher Scott Yanco said in a statement. “This creates an intriguing optimization problem that we wanted to know if cranes were solving through long-distance migration.”
[Related: Birds have ‘culture.’ Just look at these nests.]
The team studied four crane species–the common crane (Grus grus), demoiselle crane (Anthropoides virgo), black-necked crane (Grus nigricollis), and white-naped crane (Grus vipio). They all had to cross various natural barriers including the Himalayas and the Alps, Arabian desserts, and the Mediterranean Sea and experienced wildly different environmental conditions over a year.
These time periods were also synchronized with some of their important biological needs. This alignment was particularly pronounced when comparing data on air temperatures or resource availability on their wintering and summer breeding grounds. The demoiselle cranes, for example, migrated across the Tibetan plateau, and during that time had to contend with large fluctuations in temperature.
“We suspect this all has to do with different biological needs during these different times of the year,” said Yanco.
The common cranes clearly went to…
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