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.
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Breeding programs have rebuilt a population that migrates between northern Canada and the Texas Gulf Coast to more than 250 birds. An effort to reestablish an eastern population run by the Whooping Crane Eastern Partnership has been under way for 12 years. The population started at zero and now hosts more than 100 birds.Skip to next paragraph
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But these birds all have been born in captivity at the Patuxent Wildlife Research Refuge and a handful of other breeding centers. At about 6 months old, they are shipped to the Necedah National Wildlife Refuge, about 80 miles northwest of Madison, Wis., to join with other whooping cranes summering there.
There, the youngsters are trained to view an ultralight airplane as one of them, following it as it taxis around the summering grounds. When it comes time to head south, the pilot leads a migration group full of rookies. More recently, the effort has used older birds to guide groups as well.
A one-way trip to the wintering grounds at the Chassahowitzka National Wildlife Refuge, about 20 miles south of Chrystal River, Fla., is 1,140 miles.
Mueller's team used exhaustive amounts of data the Whooping Crane Eastern Partnership has gathered on each bird it has raised – including travel routes and genetic information – for its analysis of annual migrations from 2002 to 2009.
The team looked at the ages of each individual crane on each flight over the seven-year period, the age of the oldest member in a group of migrating birds, the size of each migrating group, and the genetic relationships among the birds to tease out the relative importance of innate navigation skills and those acquired by experience.
Then they looked for patterns based on how far from the straight-line path migrating groups strayed.
On average, groups of one-year-olds that included one or more older birds strayed from the straight-line course by an average of about 40 miles as they made their way south. Groups without the older birds strayed by an average of 60 miles, with about 25 percent of these groups wandering off course by nearly 100 miles.
The patterns held regardless of gender or genetic relationships among the birds.
Having an elder or two among the group also appeared to add a bit of weather wisdom. The researchers found that groups of the youngest birds that had an experienced migrator with them tended to hew closer to the straight-line course than did groups of young birds without older members. This suggested that the elders were passing along some street smarts in coping with crosswinds.
Researchers hope the cultural care-of-strangers aspect to training young whooping cranes about migration spills over into the birds' mating efforts. So far, the eastern population isn't as successful in producing offspring as conservationists had hoped.
Scientists are beginning to hunt for the reasons for that, says Converse, after returning from a whooping-crane conservation meeting in Wisconsin where sex and the single whooping crane was a significant concern.
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