Flexible Growth Rates in Nestling White-Fronted Bee-Eaters: A Possible Adaptation to Short-Term Food Shortage

Nestling White-fronted Bee-eaters (Merops bullockoides) in Kenya show an ability to slow their development rate in response to food stress and, more importantly, to recover from stress with resumption of normal development. Successful fledging occurred at ages ranging from 22-42 days. The magnitude of developmental slowing was greatest: (1) among the youngest nestlings in large broods, (2) in seasons of overall low food availability, and (3) in nests provisioned by breeding pairs alone (i.e., nests without helpers). We speculate that this ability to slow growth reduces a nestling's daily energy requirements and thereby increases its likelihood of surviving through short periods of severe food shortage.