Polyandrous Bird Moms
Female jacanas mate with multiple males, then leave each male to incubate and raise the chicks alone while she defends territory and finds more mates.
Jacanas are tropical waterbirds that have completely reversed traditional bird sex roles. Females are larger, more aggressive, and maintain territories containing multiple males.
The system works like this: 1. A female establishes a territory with 2-4 males 2. She mates with each male and lays eggs in each nest 3. Males do all the incubating (sitting on eggs) 4. Males do all the chick-rearing 5. The female defends the territory and moves between males
If a predator threatens the eggs, males will carry them to safety under their wings — one of the few birds that can do this.
This role reversal evolved because of the unusual challenges of their environment. Jacanas live on floating vegetation in tropical wetlands, where nest predation is extremely high. By having multiple males incubating different clutches simultaneously, a female maximizes her chances of successfully raising offspring.
Females are so competitive that they will kill the chicks of rival females. If a new female takes over a territory, she often destroys existing eggs and chicks, forcing males to re-mate with her instead.
This polyandrous mating system (one female, multiple males) is rare in birds but demonstrates how sexual selection can work in both directions.