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Whooping Crane Population Dynamics:
Challenges of Rebuilding an Endangered Species

 

Overview: Students keep and maintain an ongoing chart about factors that influence whooping crane population gains and losses.

Materials: Helpful materials include whooping crane biographies (available for birds in the Eastern/reintroduced flock), letters from Tom Stehn in each migration update as well as those in the Archives; selections on our Resources page, and the crane FAQ pages. Also see guiding questions on The Challenges of Whooping Crane Survival: Learning from Life Histories. You may wish to replicate the chart on large chart paper for a whole-class activity.

From One Flock to Two
In the 1940s, only 15 migrating whooping cranes stood between survival and extinction. It took over 40 years for the natural flock—the Aransas/Wood Buffalo (or Western) population—to grow from 15 to 100 whooping cranes. It took another 18 years for the natural flock to reach 200. Meawhile, a newly reintroduced Eastern flock began in 2001 with the help of ultralight airplanes to teach chicks their migration route. The Eastern flock is growing too. How many whooping cranes exist today? What causes their numbers to change from year to year? why does rebuilding an endangered species take so long?

Population Numbers: Why the Gains or Losses?
Scientists who study changes in the number and composition of individuals in a population and the factors that influence those changes are concerned with population dynamics. You'll appreciate how difficult their work is by thinking through this challenging problem yourself.

Activity
On the chart below, list all the factors you can imagine that might cause high or low numbers at each stage of the whooping crane's annual cycle:

  • Begin with the breeding season. What factors might influence the number of eggs laid (no eggs or 1 or 2 eggs)? What might cause the eggs or chicks or adults to die? What might help greater numbers to survive?
  • Next, consider the fall migration. What could cause crane deaths during fall migration? What challenges to their safe migration can you identify? (Consider both the natural flock coming from Canada and the chicks led by ultralight aircraft to Florida.)
  • Then consider mortality at the over-wintering sites, which means Texas for the natural flock and Florida for the introduced flock. What are potential causes of death there?
  • Finally, consider the spring migration. What might cause cranes to die during spring migration? What challenges can you identify?

 

Challenges of Rebuilding an Endangered Species

Breeding Season

Fall
Migration

Over-wintering
Season in TX or FL

Spring Migration

       
       
       
       
       
       
       
       
       
       
       
       
       


National Science Education Standards

Science as Inquiry
Ask a question about objects, organisms, events. (K-4)

Life Science
An organism's behavior patterns are related to the nature of that organism's environment, including the kinds and number of other organisms present, the availability of food and resources, and the physical characteristics of the environment. When environment changes, some plants and animals survive and reproduce, and others die or move to new locations. (K-4)

Science and Technology
People have always had questions about their world. Science is one way of answering questions and explaining the natural world. (K-4)

Science in Personal and Social Perspectives
Environments are the spaces, conditions, and factors that affect an individual's and a population's ability to survive and their quality of life. (K-4)

 

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