How whooping crane youngsters learn from their elders
Young whooping cranes on their first migration learn important lessons from older, more experienced birds – such as how to deal with crosswinds that could knock them off track, researchers find.
When it comes to annual migrations, young whooping cranes need old dogs to teach them new tricks – with refresher courses to keep the rookies on track.Skip to next paragraph
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That is the implication of a new study exploring the migration patterns of these majestic but endangered birds.
Such studies are important, researchers say, not only in shedding light on how large groups of animals migrate over long distances generally. Successful migration trips also help determine a species' breeding success, since the migrations take place between summer breeding grounds and winter locations where the animals can find food.
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Researchers have known for a long time that whooping cranes – long-lived, social birds – probably can't migrate successfully without some kind of early guidance, says Thomas Mueller, an ecologist at the University of Maryland in College Park who led the team conducting the study.
It's also clear that some of the birds' key migration abilities are hard-wired into them – timing, general direction, even the knowledge that they are supposed to migrate.
But which is more important, nature or nurture?
For migrating whooping cranes, the results suggest that the alarm signaling departure time for the long flight between Florida and Wisconsin is built into the birds. But their ability to know where to go once the alarm goes off appears to be the result of training.
And it turns out that it's not just a one-off course in navigation. The most striking result, Dr. Mueller says, showed that learning continued well after cranes' first migrations. The migration groups that strayed the least from a straight-line track were the groups that included the oldest birds.
Over the eight years the study covered, the modeling that the team conducted suggested that the accuracy of a group's flight path should increase by about 5.5 percent for every additional year in the oldest bird's age. For groups that included a 7-year-old bird, that would imply a 38 percent improvement over a group composed entirely of first-timers.
The team's field data suggest that at least for a crane's first five years, it indeed gets better each year at staying on course.
"There's continuous learning over many years of migration" as information is passed from the older birds to the younger birds, Mueller says.
And unlike many other bird species, the instructors aren't parents, they are complete strangers, suggesting a strong cultural component to the activity of learning, says Sarah Converse, an ecologist at the US Geological Survey's Patuxent Wildlife Research Center in Laurel, Md.
Conservation of migrating whooping cranes remains an ambitious work in progress. The birds are native to North America, but by the 1940s, the number of known individuals had plummeted to 14, Dr. Converse explains, in addition to a couple of populations of nonmigrating whooping cranes.