Figure 4.

The partial effect of experimentally measured aggression was unrelated to the probability of having a helper (having a helper indicated by one on the y-axis) at the nest in the test year for (A) breeding males and (B) breeding females. Aggression scores were defined as categorical scores ranging from one (least aggressive) to six (most aggressive). Gray lines indicate upper and lower 95% confidence intervals. Circles represent individual aggression scores and were jittered so individuals with the same aggression scores could be shown (N = 27 male and 27 female aggression scores). The model included the effects of male aggression score and female aggression score on the probability of having a cooperative helper at the nest in the test year.