The role of the visual train ornament in the courtship of peafowl, Pavo cristatus
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The peacock (Pavo cristatus) has long been considered the quintessential example of a sexually selected animal, and in the last two decades, peafowl have provided widely-cited evidence for female mate choice as well as the genetic benefits of mate preferences for ornamented males. However, previous studies have failed to reach a consensus with respect to the importance of various signaling modalities in peafowl courtship. In this thesis, I repeat two previous studies of peacock train morphology and I describe the use of light by males during their courtship displays, to clarify the role of visual signaling. I confirm previous reports that removing a large number of eyespots decreases male mating success, yet I find substantial variation in mating success among normal males that cannot be explained by eyespot number. I show that these two apparently conflicting results are not contradictory, since the removal treatment modifies males beyond the normal range of eyespot number. Next, I describe the two display behaviours used by males during courtship. When males perform their pre-copulatory “train-rattling” display, they are oriented at about 45° relative to the sun on average, with females directly in front. This directional pattern suggests that train-rattling is involved in the communication of a visual signal. The “wing-shaking” display, on the other hand, is performed with females positioned behind males, and is always elicited when a model female is positioned on the shaded side of a male. The wing-shaking display may therefore allow males to control female viewing geometry. These results indicate that mate choice in peafowl is complex, and that visual signaling is important despite recent claims to the contrary. Females may avoid males missing a large number of eyespots via a threshold-based mechanism, while choosing among full-trained males based on some other (possibly visual) cue.