Food supply and provisioning behavior of parents: Are small hoopoe nestlings condemned to die?

Abstract

Parents might use signals of need or of quality to decide food provisioning among their offspring, while the use of one or another signal might depend on food availability. Begging success of nestlings of different quality (i.e., body size) would also depend on food availability, and we here explore the effect of experimental food supply in begging success of nestlings and in provisioning of female hoopoes (Upupa epops), a species with extreme hatching asynchrony and nestlings size hierarchy. We video-recorded food allocation of females, begging success of nestlings of different size, and the social context (i.e., the size category of the other nestlings that were begging for food) during periods when experimental food supply was or was not available in the same nests. We found that when experimental food supplementation was present, begging success of the intermediate, but not that of large or small-sized nestlings, increased. The experiment, however, did not affect the feeding preferences of females toward nestlings of different size. Moreover, when small nestlings were the only ones that were begging for food, their begging success decreased in the experimental period, and females used supplemented prey to feed themselves. Those results, on one hand, confirm the importance of food availability for the begging success of nestlings of particular sizes and, on the other, indicate that females prefer to use extra food for their own rather than for the smallest nestlings. We discuss possible mechanisms explaining the detected experimental effects and the adaptive and nonadaptive explanations of mothers ignoring the small nestlings.

Parental overproduction allows siblicidal bird to adjust brood size to climate-driven prey variation

“…Functions of parental overproduction are not mutually exclusive, yet only a few studies, mostly in temperate birds, have examined and quantified them under a multiple-hypothesis approach ( Mock and Parker 1986 ; Wiebe 1996 ; Forbes et al 2002 ; Humphries et al 2006 ; Ferrer-Pereira et al 2023 ). These documented both resource-tracking and insurance benefits of marginal young to adults’ reproductive success and showed that their magnitude and relative importance could vary across and within species depending on extrinsic and intrinsic conditions.…”