Intergenerational communication and parental care in American white pelicans, Pelecanus erythrorhynchos, conflict or honesty?
Parent-offspring conflict and honest signalling theories provide distinct views of the kinds of communication systems which could evolve between offspring and their parents. Conflict theory operates under the premise that parent and young disagree over achieved levels of care while honest signalling theory assumes that parent and offspring are relatively more cooperative and mediate care provisioning with accurate information provided by young. In both field and laboratory settings I tested the extent to which conflict and honesty have shaped solicitation and care in the American white pelican (Pelecanus erythrorhynchos). Field tests examined heat and food solicitation and provisioning over the first two weeks post hatch in a natural setting. Solicitation and care patterns differed markedly between the two resources. Offspring solicitation for, and parental delivery of heat were consistent with conflict and support the possibility that parent and young can disagree over resource distribution. In contrast, the behavioural patterns associated with the solicitation and delivery of food indicate that young pelicans honestly indicate their nutritional requirements and that parents respond according to these requests. These markedly disparate patterns likely arise because of differences in the expected continuation of care. Offspring are weaned of parental heat at the ages immediately following termination of my study while food deliveries are expected to continue for several weeks. Laboratory studies explored the energetic cost of solicitation using respirometery techniques. Both conflict and honest signalling theories predict that communication by young will be costly. Solicitation for both resources was found to be energetically inexpensive with the costs for manipulative signals exceeding those for honest communication. Future research possibilities and a theoretical framework for understanding changes in communication through time are considered.