No evidence for long‐term effects of reproductive effort on parasite prevalence in great tits Parus major

Abstract

Allocation of resources between the life history traits reproduction and parasite defence are expected because both are energetically costly. Experimental evidence for such allocation has been found in short‐term effects of reproduction on parasite prevalence or immune function. However, there is increasing evidence for long‐term negative effects of reproductive effort on individuals. This study investigates whether long‐term effects of reproductive effort on parasite prevalence exist. Brood sizes of great tits Parus major were experimentally altered in one breeding season and in the subsequent breeding season the prevalence of three parasites types (blood parasites, ticks and fleas) on the surviving parents were investigated. We detected no long‐term effects of brood size manipulation on the prevalence of parasites in the next year and therefore provide no evidence for inter‐seasonal effects of reproductive effort on parasite prevalence. The post hoc level of statistical power was reasonable for effects on blood parasite and flea prevalence, but low for effects on tick prevalence.

Is parental competitive ability in winter negatively affected by previous springs’ family size?

“…We did this to prevent brood desertion when, after reduction, the family size would be less than five nestlings (Verboven & Tinbergen, 2002). To ensure that broods were disturbed to a similar extent and that the fraction of own nestlings relative to the total number of offspring remained approximately the same, we also exchanged four nestlings of the control brood, two with two nestlings of the reduced brood and two with two nestlings of the enlarged brood (for further details, see de Jong, Fokkema, Ubels, van der Velde, & Tinbergen, 2014;Fokkema et al, 2016).…”

“…Survival costs associated with defending a box could occur in the following ways: (1) directly through injuries caused by fights or (2) through physiological/behavioral tradeoffs as a result of an increased defense needed to claim a roosting box (e.g., depletion of energy reserves, changes in endocrine status, and increased predation risk; e.g., Briffa & Sneddon, 2007;Dufty, 1989;Marler & Moore, 1988). Parents that raised larger experimental broods may have suffered more injuries due to fights or the effort needed to defend their roosting box may have gone at a greater expense of their perhaps already lower energy reserves/physiological status (see Appendix S1; Drent & Daan, 1980;Verhulst & Tinbergen, 1997;Sanz & Tinbergen, 1999;Tinbergen & Verhulst, 2000;Nilsson, 2002;Nicolaus et al, 2012;de Jong et al, 2014). In turn, this could have led to the observed survival cost of reproduction.…”

Restless roosts: Light pollution affects behavior, sleep, and physiology in a free‐living songbird

“…Because restlessness by increased nighttime activity is expected to interfere with normal sleep patterns, we measured plasma concentrations of oxalic acid, a recently established cross-species marker of sleep restriction (Weljie et al, 2015). We also quantified acute phase protein concentration (Matson, Horrocks, Versteegh, & Tieleman, 2012) and malaria infection status (De Jong, Fokkema, Ubels, Van Der Velde, & Tinbergen, 2014;Piersma & van der Velde, 2012) as indices of immune function, and telomere length as an overall measure of metabolic costs and aging (Haussmann & Marchetto, 2010). In line with previous findings that link nighttime exposure to white light led to increased stress hormone concentrations and decreased immune function (Bedrosian et al, 2011;Ouyang et al, 2015), we predicted that great tits roosting closer to lampposts emitting white light would have higher activity at night, decreased haptoglobin concentration, and a higher probability of malaria infection, all leading to decreased immune function and accelerated biologic aging.…”

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

“…; for further details on manipulation scheme, see: Fokkema et al., ; de Jong et al. ). The average age of the parents that raised the manipulation groups was similar (Reduced: 1.32, Control: 1.38, Enlarged: 1.31, on a scale of 1 being a first year breeding bird and 2 an experienced breeder).…”

“…To disturb each nest to a similar extent, we also exchanged two nestlings of the reduced brood to the control brood and vice versa and repeated this procedure for the enlarged brood. For three matched trios, we exchanged two nestlings instead of three to prevent desertion of the brood by the parents (initial family size of trios: 6-7 nestlings; Verboven et al 2002; for further details on manipulation scheme, see: Fokkema et al, 2016;de Jong et al 2014). The average age of the parents that raised the manipulation groups was similar (Reduced: 1.32, Control: 1.38, Enlarged: 1.31, on a scale of 1 being a first year breeding bird and 2 an experienced breeder).…”