Sexually dimorphic breast-feathers in the Kentish Plover charadrius alexandrinus

Secondary sexual traits (such as badges and other ornaments) may signal the attractivity of a male for females, or they may reflect its parental quality. We studied the natural variation in breast-feathers in a small wader, the Kentish Plover. We hypothesised that males may have longer breast-feathers than females, because males display these feathers during courtship and male-male contests. Also, males may need longer breast-feathers to provide an efficient incubation. We measured the length of breast-feathers in both sexes and found that lateral feathers were significantly longer than the central ones in both males and females. We also found that breast-feathers tended to be longer in males, especially the central ones, than in females. The mean length of breast-feathers decreased over the breeding season in males, although this relationship was not significant in females. Taken together, our results suggest a moderate difference in breast-feathers between the sexes. We suggest that this difference is due to sexual selection and/or natural selection to achieve more efficient incubation of the eggs.