Context-dependent effects of an experimental increase of hunger level in house sparrow nestlings

Abstract

Exploring the links between parental supply and nestling demands and between nestling demand and food supply is of central importance for understanding the evolution of parent-offspring communication. It has been suggested that optimal food supply by parents and begging effort of nestlings are context dependent, and we here test some predictions of this hypothesis. House sparrow (Passer domesticus) nestlings were experimentally fed with a pharmacological appetitive stimulant (cyproheptadine) that increases nestling demands, and explore its effect on nestling growth (i.e. body mass and tarsus length), which can be considered as the net payoff of inflated and costly offspring demand. As assumed by the experimental protocol, nestlings with an exaggerated demand were preferentially fed by parents. In accordance with the hypothesis, net benefits in terms of growth were mainly detected in first breeding attempt of parents that successfully reared three broods. Because costs associated with parental feeding should be lower for first breeding attempts and for parents of higher phenotypic quality (those able to successfully rear three clutches), our results provide to our knowledge, the first experimental evidence supporting a dynamic role of costs of food supply affecting net payoff of offspring demands, which may help to understand the mechanisms allowing the evolutionary equilibrium between intensities of offspring begging and parental provisioning. Significance statementBoth feeding and begging for food are costly activities for offspring and parents respectively. Rewards of such behaviours in terms of food receiving and reproductive success should vary depending on ecological conditions (i.e. food availability for offspring and physical condition of parents). Here we pharmacologically exaggerated appetitive of house sparrows (Passer domesticus) nestlings and explore its effect on parental behaviour and on nestling growth (i.e. body mass and tarsus length). The expected benefits were mainly detected for first breeding attempts and only in nests of adults that were able to rear two more broods, that is, when costs of feeding the offspring by adults are lower. Our results provide to our knowledge, the first experimental evidence supporting dynamic outcomes of offspring demands and parental provisioning, which is essential for understanding the evolution of parent-offspring communication.

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

“…As it occurs for some other bird species ( Ruiz-Castellano et al 2016 ; Soler et al 2017 ; Brode et al 2021 ), food provisioning by female hoopoes will largely depend on social context (i.e., characteristics of the group of nestlings that are begging for food at a particular feeding event). Since we know that hoopoes prefer to feed larger offspring, the expected positive effects of extra food on feeding rates of small nestlings should mainly occur when larger nestlings are satiated and do not beg for food ( Parker et al 2002 ).…”

Coloration of spotless starling nestlings shows genetic and environmentally determined characteristics while begging for food

“…Thus, begging‐related signals should mainly be environmentally determined. Similarly, parents respond to offspring needs would also depend on food availability and, therefore, also be environmentally influenced (Bize et al., 2006; Boncoraglio et al., 2013; Mock et al., 2011; Ruiz‐Castellano et al., 2016). Consequently, mainly because begging‐related traits are by definition signals of needs, most should be environmentally determined with very little genetic influence if any (Casagrande et al., 2009; Dugas, 2012).…”

Great spotted cuckoos respond earlier to the arrival of feeding foster parents and perform less erroneous begging when hungry than their magpie host nest‐mates

“…Begging signals are emitted by nestlings to solicit food from their parents and are considered to be honest signals because they entail several physiological costs (Kilner 2001, Noguera et al 2010, Martín-Gálvez et al 2011, Moreno-Rueda and Redondo 2011, Soler et al 2014a. Consequently, parents regulate their effort and resource allocation according to the conspicuousness and intensity of the begging displays (Price and Ydenberg 1995, Kilner and Johnstone 1997, Budden and Wright 2001a, Leonard and Horn 2001, Quillfeldt et al 2006, Budden and Beissinger 2009, Martín-Gálvez et al 2011, Ruiz-Castellano et al 2016. As such, parents often preferentially feed the nestlings with the most intensive begging displays (Dearborn 1998, Lichtenstein and Sealy 1998, Leonard et al 2000, Roulin et al 2000, Hauber et al 2001, Leonard and Horn 2001, Roulin 2002, but also the first nestling that starts to beg is usually fed before its nest-mates (Roulin 2001, Leonard et al 2005, Porkert and Spinka 2006.…”

“…Brood parasite nestlings are known to have more conspicuous begging calls than non‐parasites (Soler et al , 1999, Davies et al , Dearborn , Lichtenstein and Sealy , Kilner and Davies , Kilner et al , Dearborn and Lichtenstein , Rodríguez‐Gironés et al , Rivers , Grim 2008, Soler ). This general pattern is usually explained based on the fact that brood parasitic nestlings are not related to either their nest‐mates or their foster parents, and so they are not constrained by inclusive fitness costs by depriving present (or future) siblings from food (Briskie et al , Rivers and Peer ).…”