nesting hollows are relatively rare within the eclectus’ habitat, and can be very difficult to find. As such, females tend to monopolize good nesting hollows once found, staying there up to 11 months a year, and returning to the same nest at times for multiple years. Females have been known to fight off other females, sometimes to the death, to defend their nesting hollows. Males have been known to travel unusually large distances to mate with females, the longest found being 7.2 kilometers (4.5 miles). Eclectus parrots are unusual among parrots because they exhibit both polyandrous mating (females mate with multiple males) and polygynandrous mating (males mate with multiple females and females mate with multiple males). Even more unusual, these birds exhibit a form of polyandry known as cooperative polyandry, in which multiple males breed with a single female, and all the males work together to help the female raise the chicks, rather than compete with each other. They are the only parrot known to do this. Females will lay 2 eggs per clutch, but often only fledge 1 young. Eclectus are also unusual in that they can bias the sex of their offspring, such that they can manipulate whether their offspring are male or female. It is thought that this behavior occurs as a result of the scarcity of their nesting hollows. As such, females will only have male offspring when resources are plentiful, a good nesting hollow is secured, and many males are around to feed her and her offspring, as male offspring are more energetically expensive to raise as compared to females. References External links Eclectus researcher Robert Heinsohn's website Eclectus photo collection from Drexel University More information on the intersection of sexual selection and ecology Eclectus roratus species fact sheet Eclectus infectus species fact sheet Psittaculini Bird genera Bird genera with one living species