Parental response to elevated begging in a high predation, tropical environment

Interactions among parents, offspring and the environment are a critical aspect of parental care. Begging by offspring usually results in increased parental provisioning. Yet, parents also vary their behaviours to reduce offspring predation. Both begging sounds and provisioning activity can increase risk of nest predation. We predicted in a high nest-predation environment, parents would satiate young and reduce begging by increasing food load but maintaining the same provisioning rates. We also assessed whether increased begging was beneficial to offspring and whether parents changed the allocation of food to particular nestlings. We increased whole-brood begging via playbacks at nests of a tropical passerine bird, the western slaty antshrike, Thamnophilus atrinucha. We observed that parents increased provisioning rates and reduced food load in response to elevated begging. Selection may therefore favour feeding hungry nestlings even when predation risk is elevated, or begging sounds may place offspring at a higher risk than increased activity. Parents reduced the time between arrival to the nest and feeding of nestlings, potentially to reduce begging sounds. Exaggerated begging did not appear to be beneficial to offspring since parents did not deliver more food. Parents switched to preferentially feed the closest offspring during the begging treatment. This suggests that, under elevated begging, parents either allowed sibling competition to influence feeding decisions, or fed the closer nestling to reduce the time between arrival to the nest and feeding. Studying species in different environments provides insight into how ecological factors such as nest predation influence parental behaviour.