American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Elder barn owl nestlings flexibly redistribute parental food according to siblings’ need or in return for allopreening”

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Pauline Ducouret, Andrea Romano, Amélie N. Dreiss, Patrick Marmaroli, Xavier Falourd, Manon Bincteux, and Alexandre Roulin (July 2020)

Allofeeding can be driven by kin selection and reciprocity, and depends on environmental conditions in barn owl chicks

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Sibling barn owls (<i>Tyto alba</i>).<br/>(Credit: Amélie N. Dreiss)
Sibling barn owls (Tyto alba).
(Credit: Amélie N. Dreiss)

Abstract

Kin selection and reciprocation of biological services are distinct theories invoked to explain the origin and evolutionary maintenance of altruistic and cooperative behaviors. Although these behaviors are considered as non-mutually exclusive, the cost-to-benefit balance to behave altruistically or to reciprocally cooperate, and the conditions promoting a switch between such different strategies have rarely been tested. Here we examined the association between allofeeding, allopreening and vocal solicitations in wild barn owl (Tyto alba) broods under different food abundance conditions: natural food provisioning, and after an experimental food supplementation. Allofeeding was mainly performed by elder nestlings (hatching is asynchronous) in prime condition, especially when the cost of forgoing a prey was small (when parents allocated more prey to the food donor and after food supplementation). Nestlings preferentially shared food with siblings that emitted very intense calls, thus potentially increasing indirect fitness benefits, or the ones that provided extensive allopreening to the donor, thus possibly promoting direct benefits from reciprocation. Finally, allopreening was mainly directed towards older siblings, perhaps to maximize the probability of being fed in return. Helping behavior among relatives can therefore be driven by both kin selection and direct cooperation, although it is dependent on the contingent environmental conditions.