M matrix Bird 2
Cooperate      Defect
Bird Cooperate
R
4, 4		 S
1, 1
T
1, 1		 P
0, 0
1 Defect
 
 
 
P matrix Bird 2
Cooperate      Defect
Bird Cooperate
R
3, 3		 S
0, 5
T
5, 0		 P
1, 1
1 Defect
 
 
 
 
 
 
The P matrix and the M matrix.

The first number in each cell represents the payoff to bird 1, the second number the payoff to bird 2.

In the M (byproduct mutualism) matrix, there is no temptation to defect, as cooperating always fared better than defecting (4 > 1, 1 > 0).

The P (prisoner's dilemma) matrix should also encourage reciprocity, provided the birds follow a strategy such as tit-for-tat.