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How Can You Tell Male and Female Eagles Apart?
Student Worksheet

In many bird species, it's easy to tell males from females because the plumage is different. Not so with eagles! However, we can use size measurements from different parts of the eagle's body to determine the gender of the eagles we capture. Female eagles generally have larger wings, feet, talons, beak, etc. A biologist by the name of Bortolotti discovered that 2 size measurements show the greatest separation of male and female. The two measurements are:

  1. beak depth and
  2. hallux (toe claw) length

These measurements can be used in the following formula:

Sex = (bill depth x 0.392) + (hallux length x 0.340) -27.694

  • If the answer is POSITIVE, the eagle is a FEMALE.
  • If the answer is NEGATIVE, the eagle is a MALE.

Here are the key measurements from 6 eagles, plus their weights. Can you determine the gender of these birds yourself?

Eagle

Weight (kg)

Bill Depth (mm)

Hallux Length (mm)

Gender

K58

 

5.5

37.9

44.5

 

K72

 

6.6

35.9

42.7

 

E47

 

6.7

35.0

42.2

 

E49

 

6.1

35.5

42.7

 

E63

 

4.5

32.6

40.5

 

E50

 

5.1

32.4

41.2

 

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