Bronze-winged Jacana - Mating System

Mating System

Bronze Winged Jacanas have a territorial, sex-role reversed system. They are polyandrous, and the females are larger and more brightly colored than their male counterparts. The females compete with each other for harems of males to incubate their clutches of eggs. Each female’s territory encompasses one to four males and their individual territories. The density of breeding territories can be limited by habitat availability and the territorial competition with other females and their harems. Although there is no clear evidence for a relationship between male territory size and the distribution of available resources, heavier males have been shown to defend their territories from other males. The overall distribution of territories appears to be small areas controlled by individual males, with the harems of females encompassing one or more of the male territories. Even though the territory size of females is positively correlated with the size of their harems, it does not seem to be related to the overall quality of the habitat. Females could attempt to maximize harem size by including as many male territories as they can, while males in larger harems would have to defend smaller territories. As a result, the degree of polyandry of the Bronze Winged Jacana is dependent on the territory sizes of males and females.

The breeding system of the Bronze Winged Jacana leads to intense sperm competition, as female jacanas copulate with multiple males prior to laying their clutch. Before laying the clutch, the female would spend more time with the specific male that would receive the clutch (called the “receiver”). Studies have also shown that receivers gain more copulations than non-receivers. Since the receivers provide all of the parental care, females should, in theory, comply with male demands for copulations to convince them of their paternity, so they will care for the clutch. Receivers have been observed to destroy clutches in which they only had a low share of the paternity. Although females offer copulations to non-receiver males in order to maintain their presence in her harem, these copulations are less important than copulations to assure the receivers of their paternity. The cost of clutches being destroyed by receivers is much higher than losing males from her harem.

Since the males have no individual control over the maximum number of their copulations, the males in polyandrous harems vie for the female’s attention through a call, called a “yell,” to attract her and gain sexual access. It has been shown that male jacanas in larger harems yelled at higher rates during the periods of time when all copulations took place, while males that already received their clutch or were involved in chick care yelled at lower and rates. These yells attracted the female Bronze Winged Jacana when she is far from the yeller. A study showed that females seem to use yells to assess male quality, as the males that yelled at the highest rates were able to receive the greatest number of copulations. Females may also respond to the yells of males in their territory since they could attract other females who could intrude on their territory.