 Efforts are now underway to repopulate islands formerly inhabited by tortoises to restore their ecosystems (island restoration) to their condition before humans arrived.The tortoises are a keystone species, acting as ecosystem engineers which help in plant seed dispersal and trampling down brush and thinning the understory of vegetation (allowing light to penetrate and germination to occur).Birds such as flycatchers perch on and fly around tortoises to hunt the insects they displace from the brush.