 Juveniles have lower foraging efficiency compared to adults and in most feeding flocks , the juveniles are usually outnumbered by the adults . They usually tend to stay close to one another and forage for food together at the peripheral region of the group . During the breeding season , adult male ibises have been recorded raiding other parent ibises who are feeding their young in the colony . The raiders force their bill down the throat of the victim — either the parent about to disgorge their food or recently fed young — and extract the ball of food . This behavior allows the otherwise starving adult males to obtain food without having to spend long periods of time away from the nest , and prevent its female mate copulating with another male ibis , which would reduce its own reproductive success . Females and juveniles almost never try to drive off the larger and more aggressive pirating males , but instead try to avoid or move away from them . This pirating behavior is less common between two male ibises as the males will actively fight off the pirate . The explanation of the species ' sexual dimorphism of body size is unclear , because no differences between the sexes in feeding success rates or the foraging behavior have been observed and , as males are larger , they need more food than females . 
