Who Goes Where? Dividing the Flock

In 2008 for the first time, the team split the birds into two groups headed for two wintering areas: the original winter home at Florida's Chassahowitzka NWR and a second home at Florida's St. Marks NWR.

Dividing the Flock

Why split the group? There are many threats to Whooping cranes; both the Whooping Crane Recovery Team and the Whooping Crane Eastern Partnership wanted to test a new site by dividing the flock. They could not forget loss of 17 of the 18 Class of 2006 cranes at Chass after a severe storm in February 2007. More crane habitat is available at St. Marks and storm-driven tides are rare. Splitting the flock between the two sites is wise. It allows a new site to be tested without putting all the birds at risk. At the same time it cuts the risk of another loss of an entire generation such as happened with the Class of 2006. With so many adults in the flock now, they believe it will be safer for the crane-kids to have more space and privacy from the territorial older birds. (The older birds often return to "their" winter pen site for free food — or to pick on the youngest birds.)

How will the team decide who goes where? They consider five important factors: gender, siblings, dominance, genetic value, and migration knowledge. That means:

  1. Each group should have the same number of females.
  2. Any siblings of the opposite gender will be kept together; siblings of the same gender will be apart.*
  3. Birds in each group must get along with one another and have a balanced dominance order. Birds with social problems must be evenly divided or separated.
  4. Genetically valuable birds must be evenly divided.
  5. Birds that missed parts of the fall migration due to dropping out or not being able to fly on some of the fly days should be evenly divided.

Try This: Journal or Discussion Questions
  • The group that winters at Chass will need to fly a greater distance in the spring than the group from St. Marks. Could this affect the decision of how the birds are divided? If so, how?
  • Which of this year's" ultra-cranes" would you put into each of two groups? See what the Team decided >>
  • The final decision for which birds go in each group will be made by a teleconference call among WCEP experts when the Team nears the end of migration. Why do you think many opinions are being considered?
  • *Scientists have to do some guess work. Some experts believe it is more important to split any brother-sister cranes. Then if something bad happens to one group, the whole family isn't lost together. Because they were reared together, the brother and sister would view each other more as siblings and not be likely to pair with each other later. Others say it is more important to separate siblings that are the same gender. Why is the question of gender of such great concern? How might the scientists get more information to help their decision making?
  • When your teacher assigns seats or groups in your classroom, how do you think those choices are made?