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Overview

Teacher's
Section

DNA Extraction for Cheek Cells

Preparing DNA for Analysis by Gel Electrophoresis

Nesting Behavior: Harri's Hawks

Student
Activity

Materials List

Resource List

Using Genetic Evidence
to Evaluate Group Behavior

Classification of Individual Roles

Below is a list of jobs associated with each role.

• The Alpha birds are the dominant adult birds. They provide most of the care for the nestlings. Remember that there is always one Alpha Female and one Alpha Male at each nest.

• The Beta birds are subordinate adult birds. They hunt, protect the nest, and participate to a lesser degree in all nesting behavior. There may be more than one Beta male or female at each nest.

• The Gamma birds are juveniles, often remaining from the previous year.

Behavior	Alpha	Beta	Gamma
Participate in group hunts	+	+	+
Provide prey	+	+	+
Detect predators	+	+	+
Harass predators	+	+
Provide nest material		+
Build nest	+
Incubate, brood and shade nestlings	+
Feed nestlings	+

Below is a chart showing the percentage of successful and unsuccessful capture attempts (n=259 observations) by Harris' hawks hunting alone and in groups.

Outcome of Capture Attempts	1	2	3	4	5
Successful	20.0%	32.1%	40.4%	37.9%	50.0%
Unsuccessful	80.0%	67.9%	59.6%	62.1%	50.0%
Unknown	26	11	5	4	6
Number of Observations	91	64	57	33	14

Hunting success increases dramatically when the Hawks hunt together. Prey is shared amonggroup members (from the same nest) and with the nestlings.

Age	# of Male Disperses	# of Female Disperses	Alpha Male Unrelated Group	Alpha Female Unrelated Group	Beta Male Unrelated Group	Beta Female Unrelated Group
1st Year	3	5	0	0	3	5
2nd Year	3	3	0	1	3	2
3rd Year	7	5	0	3	7	2
4th Year	4	1	0	1	4	0
Total (%)	17	14	0	5 (36%)	17 (100%)	9 (64%)

Female fledglings left the nest sooner than male fledglings. They were also more likely to become a dominant (alpha) bird in their new nesting group. None of the male fledglings that were followed held a dominant role in their nesting group.

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