HELPING-BEHAVIOR IN COOPERATIVELY-BREEDING GREEN WOODHOOPOES - SELECTED OR UNSELECTED TRAIT

1. I experimentally examined components of the stimulus-response mechanism and their effects on feeding rates to nestlings in cooperative singular-breeding green woodhoopoes Phoeniculus purpureus, and showed that both auditory and visual stimuli played important roles. 2. Breeding status did not influence the way in which adults responded to the various stimuli. 3. Adult woodhoopoes fed foreign nestlings which had been transferred as frequently and with as much food as their own nestlings. 4. Observational evidence from two different studies showed that recent-immigrant nonbreeders provided young with as much food as other established nonbreeders. Thus, there is no evidence that nonparental feeding behaviour is related to nest-site specificity, kin discrimination, or prior association with breeders in this species. 5. Demographic data gathered over a period of eight years (1981-1989) for a total of 258 ''group years'' suggested that helpers did not gain any direct or indirect fitness benefits as a result of their nonparental feeding contributions to young per se.