Reproductive effort and future parental competitive ability: A nest box removal experiment.

Rienk W Fokkema,Richard Ubels,Joost M Tinbergen,Christiaan Both,Livia De Felici

doi:10.1002/ece3.4342

Rienk W Fokkema, Richard Ubels + Show 3 more

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https://doi.org/10.1002/ece3.4342

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Abstract

The life history trade‐off between current and future reproduction is a theoretically well‐established concept. However, empirical evidence for the occurrence of a fitness cost of reproduction is mixed. Evidence indicates that parents only pay a cost of reproduction when local competition is high. In line with this, recent experimental work on a small passerine bird, the Great tit (Parus major) showed that reproductive effort negatively affected the competitive ability of parents, estimated through competition for high quality breeding sites in spring. In the current study, we further investigate the negative causal relationship between reproductive effort and future parental competitive ability, with the aim to quantify the consequences for parental fitness, when breeding sites are scarce. To this end, we (a) manipulated the family size of Great tit parents and (b) induced severe competition for nest boxes among the parents just before the following breeding season by means of a large‐scale nest box removal experiment. Parents increased their feeding effort in response to our family size manipulation and we successfully induced competition among the parents the following spring. Against our expectation, we found no effect of last season's family size on the ability of parents to secure a scarce nest box for breeding. In previous years, if detected, the survival cost of reproduction was always paid after midwinter. In this year, parents did pay a survival cost of reproduction before midwinter and thus before the onset of the experiment in early spring. Winter food availability during our study year was exceptionally low, and thus, competition in early winter may have been extraordinarily high. We hypothesize that differences in parental competitive ability due to their previous reproductive effort might have played a role, but before the onset of our experiment and resulted in the payment of the survival cost of reproduction.

Highlights

One of the corner stones of life-history theory is the cost of reproduction: an increase in current reproduction goes at the expense of fitness that will be gained from future reproduction (Barnes & Partridge, 2003; Williams, 1966)
We found no evidence for a negative effect of family size on the ability of parents to claim a roosting box, but in spring we did find that manipulated family size negatively affected the ability of Great tit parents to claim a preferred deeper nest box
In a follow-up study focused on Blue tits (Cyanistes caeruleus), we found that deeper nest boxes offered higher breeding success, especially in areas with high predation pressure (Fokkema et al in press)

Summary

Introduction

One of the corner stones of life-history theory is the cost of reproduction: an increase in current reproduction goes at the expense of fitness that will be gained from future reproduction (Barnes & Partridge, 2003; Williams, 1966). The focus of most studies has primarily been on physiological mechanisms behind fitness costs of reproduction These studies show that reproductive effort entails physiological costs as depletion of energy stores, depletion of micronutrients, physiological stress, oxidative stress, immunosuppression, and costs to maintain neuroendocrine control systems (discussed in: Alonso-Alvarez & Velando, 2012). While these physiological mechanisms tell us something about how the cost of reproduction are being paid, they do not answer why in some study populations costs of reproduction have been detected and not in others. Knowledge of the ecological mechanisms likely provides more insight in the occurrence of costs of reproduction

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