Fig 1.
An experimental set-up using a peephole to assess the behaviour of inbred and outbred males in response to a mating opportunity.
A cage was divided into two compartments using a cardboard wall that contained a small peephole. Males could only obtain visual access to the female on the other side of the cage by positioning themselves in front of the peephole on perch A. Only one male at the time could occupy this position, which could elicit competition. Perch B did not allow visual access to the female and served as a control position in the cage.
Table 1.
A description of the behavioural parameters that were scored during the time inbred and outbred males were exposed to a female behind a peephole.
Table 2.
The results of the PCA analysis in order to group behavioural parameters that were observed during the time inbred and outbred males could obtain visual access to a female by positioning themselves in front of a peephole.
PC1 was interpreted as displacement behaviour, PC2 as avoidance behaviour and PC3 as aggressive behaviour.
Fig 2.
Parameter estimates with confidence intervals of Markov chain Monte Carlo generalized linear mixed models.
The effects of inbreeding and body condition on aggression, avoidance and displacement behaviour, and on the time spent peeping, the total time spent on perch A and on perch B. The time spent peeping was significantly affected by inbreeding as shown by the confidence interval not overlapping with zero.
Fig 3.
Peeping behaviour of inbred and outbred males with each data point representing a dyad of an inbred and an outbred male.
During 60 minutes of being exposed to a female that was accessible visually by perching in front of peephole, inbred males positioned themselves significantly more time in front of the peephole to peep at a female on the other side of the cage than their outbred opponents. This result remained significant after rerunning the analysis without the dyad indicated with a star.
Fig 4.
The covariation of aggression, avoidance and displacement behaviour with the time spent peeping, the time spent on perch A and the time spent on perch B. The PC scores of avoidance and aggression were multiplied by -1 for easier interpretation of the covariance. The time spent peeping and the total amount of time males spent on perch A, where birds could position themselves in front of the peephole to look at a female, tended to show positive covariation with aggression, and negative covariation with avoidance. The time birds spent on perch B, a control position in the cage that did not enable visual access to a female, tended to show positive covariation with the expression of behaviours indicative of avoidance.