The early maternal environment shapes the parental response to offspring UV ornamentation

Jorge García-Campa,Judith Morales,Wendt Müller,Ester Hernández-Correas

doi:10.1038/s41598-021-00251-4

Abstract

Parents allocate resources to offspring to increase their survival and to maximize their own fitness, while this investment implies costs to their condition and future reproduction. Parents are hence expected to optimally allocate their resources. They should invest equally in all their offspring under good conditions, but when parental capacity is limited, parents should invest in the offspring with the highest probability of survival. Such parental favouritism is facilitated by the fact that offspring have evolved condition-dependent traits to signal their quality to parents. In this study we explore whether the parental response to an offspring quality signal depends on the intrinsic capacity of the parents, here the female. We first manipulated the intrinsic capacity of blue tit (Cyanistes caeruleus) females through lutein-supplementation during egg laying, and we subsequently blocked the UV/yellow reflectance of breast feathers on half of the nestlings in each brood. We did not find evidence that the female intrinsic capacity shaped parental feeding or sibling competition according to offspring UV/yellow colouration. However, nestling UV/yellow colour affected costly behavioural interactions in the form of prey-testings (when a parent places a prey item into a nestling’s gape but removes it again). In lutein-supplemented nests, fathers but not mothers favoured UV-blocked chicks by testing them less often, supporting previous results. Accordingly, in lutein-supplemented nests, UV-blocked nestlings gained more mass than their siblings, while in control nests we found the opposite effect and UV-blocked nestlings gained less. Our results emphasize that the prenatal environment shaped the role of offspring UV/yellow colour during certain family interactions and are indicative for sex-specific parental care strategies.

Highlights

Need to both parents[20] and siblings[21]
Evidence suggests that parents favour nestlings with enhanced UV colour as the breeding season progresses—once the resources become limiting[25]. It has been little explored experimentally whether parents favour specific offspring within a brood according to both the expression of offspring UV coloured signals and their own parental capacity, which is mainly constrained by resource availability
We investigate whether parental care preferences change with the expression of an offspring quality signal, and whether parental preferences for signal expression vary with the rearing capacity of the parents

Summary

Introduction

Need to both parents[20] and siblings[21]. During these family interactions offspring may display conspicuous structural traits such as colourful scales, gapes or feathers to trigger a parental r esponse[22,23]. We experimentally manipulated in half of the nestlings within each brood a nestling quality signal, the UV/yellow breast plumage c olouration[35] This trait mediates costly behavioural interactions among family-members, since blue tit nestlings with experimentally reduced UV reflectance beg more during parent–offspring and sib-sib competitive events and are in lower c ondition[29]. When conditions are harsh, fathers but not mothers respond to offspring UV colour by performing more prey-testings, which occur when parents introduce a prey item in a nestling gape and withdraw it again This behaviour has been interpreted as a way to assess individual offspring need or hunger levels (see “Behavioural variables” section below) and as food is withdrawn, it imposes a cost to chicks in terms of reduced body mass g ain[29]. We expected UV-blocked nestlings to beg more, as previously found in our study p opulation[29], and especially so in control nests, in which the females’ rearing capacity was more limited

Methods

Results

Conclusion