Monday, March 22, 2010

A Change of (Recovery) Plans for Whooping Cranes?

A major goal of the Whooping Crane recovery plan has been the establishment of a self-sustaining migratory eastern flock. At one point, wild Whooping Cranes had been reduced to a single population, the one that now winters in Aransas NWR. That situation would leave the species vulnerable to a natural disaster, epidemic, or other event that could decimate the flock and push it towards extinction, so a second flock is necessary for the long-term good of the species. Creating that second flock from captive-bred birds has proven difficult and expensive. The latest setback is that the proxy summer grounds may need to be moved from Necedah NWR in Wisconsin. Multiple crane pairs have been abandoning their nests, most likely due to swarms of black flies.
Clemency said the chief culprit appears to be marauding black flies - specifically, a species of the insect attracted to birds, not humans.

Research in 2009 by scientists from Clemson University revealed that black flies tend to congregate where the cranes nest. Traps caught few of the flies elsewhere on the refuge, "but thousands of black flies were observed at whooping cranes' nests," after the birds gave up and left, Clemency said.

The researchers found that the flies travel as far as five or six miles to be near the cranes. Why? It's not clear, but Clemency said possible attractions are the birds' feces or hormonal secretions. Scientists don't see black flies hassling cranes in Canada.

This spring, the partnership will experiment with using a naturally occurring soil bacterium to control the flies in the Yellow River.

Also, for the first time researchers will be training high-resolution cameras on nests to see what happens next month, when cranes in past years have left their nests.

"This will give us details not only of the birds in the nest, but we'll be able to see how many flies are on the heads of the birds," Clemency said.

"Frankly, at times it's baffling," Hartup said, but as troubling as it is, "the thing is, it requires a good deal of patience."

Many of the nesting birds will be 6 to 8 years old this spring. In the life of a crane, the birds are still young, inexperienced parents, he said. Some are struggling to pair off; others have lost mates. Also, the birds were born and raised artificially, and he said this might affect their habits as young adults.

The only crane born in the wild in the Eastern flock was in 2006.
A possible destination is Horicon NWR, also in Wisconsin, which may have a lower black fly population than Necedah.