Science & Environment

Older cranes help keep younger birds on the right track

Whooping crane
Image caption The more frequently a crane flew the route, the straighter the line it took in following years

A study of whooping cranes has shed new light on how much of a bird's migration route is learnt, and how much is innate in its genetics.

Scientists found that learning from older, more experienced birds was a crucial factor in the migratory habits of this long-lived, social species.

The US-German team of researchers also found that the cranes' migratory performance improved over time.

Details of the research have been published in the journal Science.

In other bird species, genetics has been shown to play a significant role in the timing and direction of migration.

Back from the edge

After being pushed to the brink of extinction by unregulated hunting and loss of habitat, whooping cranes are starting to spread their wings across the skies of North America.

Nine years ago, the Necedah National Wildlife Refuge in the US state of Wisconsin took a group of captive-bred whooping cranes and taught them their ancestors' migration route.

The birds followed the dulcet sounds of crane calls, which were emitted from a piloted ultra-light aircraft across nearly 1,500 miles of sky from Wisconsin to Florida.

After the initial training, the whooping cranes began to migrate to and from their breeding grounds freely in groups.

Image caption A piloted ultra-light aircraft was used to "train" the captive-bred birds

Researchers examined the data from these birds' migration paths and found that the presence of older, more experienced birds helped the migratory group stay on a straight-line course to their breeding grounds.

Moreover, the more frequently a crane flew the route, the straighter the line the crane took in following years.

"The research shows that learning of migration happens over many years and that social learning plays an important role as younger birds are able to learn from older birds," said Dr Thomas Mueller, an ecologist at the University of Maryland and lead researcher on the project.

"It is very possible this applies to other bird species that are long-lived and are social. Any bird that lives for many years and migrates in groups potentially has an important learning process."

The researchers were not able to detect a genetic component to the cranes' migratory habits in this study. But they say that previous evidence suggests that innate behaviour must play a role in some aspects of crane migration.

The team says their results have important implications for conservation and recovery efforts focused on whooping cranes, and potentially other long-lived, social birds such as storks and geese as well.

"Because experience is really paying off in migration, we need to be patient in other aspects of the recovery of these species such as the focus on why these birds have trouble reproducing in the wild," said Dr Bill Fagan, the chair of the department of biology at University of Maryland and who works with Dr Mueller.

"That may need to be learnt as well."

More on this story

Related Internet links

The BBC is not responsible for the content of external Internet sites