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Analyzing the Whooping Crane Population Data


Click graph to enlarge


How is the world's last remaining natural migratory flock of Whooping cranes doing? The population figures in the table below show the growth of this flock.

Activity: Make Three Graphs
Show changes in the population levels for the only natural migratory flock (the Aransas/Wood Buffalo/Western flock) of this endangered species. Use the population data below to make 3 graphs:

  • The number of Whooping Cranes per year.
  • The increase in the number of Whooping Cranes per year.
  • The percent increase in the number of Whooping Cranes per year.

Population of Whooping Crane Natural Flock (Aransas/Wood Buffalo Flock)
1940-Present*
(Winter Counts)
Year # Cranes Year # Cranes
1940

22

2000

177

1950

34

2001

174

1960

33

2002

185

1970

56

2003

194

1980

76

2004

216

1990

146

2005

218

1991

132

2006
237
1992

136

2007
266
1993

143

2008
270
1994
133
2009
263
1995

158

2010
281
1996
160
2011
*245 +?
1997

182

2012
**279
1998
183
2013
***304
1999
185
2014  

*The winter 2011-12 count presented many challenges to getting an accurate total. Warm weather and extreme drought conditions on the Texas wintering grounds in winter 2011-02 are believed to have caused much wider dispersal of cranes, making a direct count difficult. Whoopers that normally remain on or near Aransas NWR were detected in Nebraska, Kansas, Oklahoma, and eight counties in Texas. Officials had hoped for 300 Whooping cranes to migrate south after the 2011 breeding season in Canada.

**The winter 2012-13 count was not finalized until March 2013, and it was based on a new method. Bologists at Aransas NWR have switched from direct count to estimates.

***In December 2013 the peak population size of the western flock on the primary wintering grounds was estimated as 304 birds (95% confidence interval [CI] 260–364), and additional birds were located outside the survey area. Whooping cranes faced challenging conditions due to forest fires during the 2013 breeding season and continued drought during the wintering season Texas.


Try This! Discussion or Journaling Questions
  • After making your 3 graphs, describe the different visual picture each graph gives you. Was it helpful to graph the data in these different ways?
  • Think about what each graph means. What different information does each graph show you? Give each graph a title.
  • Which graph do you think is the most revealing?
  • Are there times when the numbers appeared to increase significantly, but the percentage increase was not as pronounced?
  • What questions did the graphs make you think of about the climb in population size?
  • What reasons do you suppose are behind these population changes? List all the factors you can think of that might have caused the population to rise (or fall) as the data show.
  • During which decade did the population increase at the fastest rate? Which year did it increase the most?


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