By Victoria GillScience reporter, BBC News
12 December 2017
Golden eagles in North America may have the timing of their migration shifted out of step with a seasonal boom in food they need to raise their young, according to scientists.
A project to track the impact of climate change on migrating animals has revealed that adult golden eagles are unable to shift the timing of their migration.
Lead researcher Scott LaPoint from Columbia University presented the findings at the annual meeting of the American Geophysical Union.
He explained that day length, or photoperiod, appeared to give the great birds the cue to go "as far and as fast as possible".
When analysing tracking data, composed of 20 years' worth of tagging birds with satellite tags and following their seasonal migrations, Dr LaPoint noticed an unusual pattern. Younger raptors would shift the timing of their journey, seemingly adapting to weather conditions and climate.
"But the adults get this photoperiod trigger and it's 'Time to go!'," he told BBC News.
"I would have expected an older, wiser bird to better time their migration," he added.
"But, with thesis [daylight] trigger, they don't have the luxury of deciding. They need to get [to their nesting site] as soon as possible to initiate a clutch.