Immune challenge reduces begging behavior and modifies begging call structure in spotless starling nestlings

Symptoms of illness offer insights into an organism’s condition, altering
social signals that affect others' behavior. Nestling birds employ
begging signals to solicit parental care, but the extent to which begging
reflects nestling health beyond hunger remains controversial. We
investigated how experimentally induced changes in health affect begging
signals in spotless starling (Sturnus unicolor) nestlings. To alter health
status, we administered an immune challenge by injecting
lipopolysaccharide (LPS) or a control substance (PBS) and observed begging
behavior under controlled food deprivation conditions. LPS-treated
nestlings exhibited delayed gaping, reduced stretching, and less begging
time compared to control nestlings. Moreover, LPS-treated nestlings
produced calls with higher spectral entropy, particularly when deprived of
food for longer. Our findings indicate that begging signals are sensitive
to induced sickness. However, addressing mechanistic issues is crucial for
effectively testing whether begging reflects nestling conditions as a
signal of quality in future experimental setups.