A pre‐breeding immune challenge delays reproduction in the female dark‐eyed junco Junco hyemalis

Abstract

Precise timing of life‐history transitions in predictably changing environments is hypothesized to aid in individual survival and reproductive success, by appropriately matching an animal's physiology and behavior with prevailing environmental conditions. Therefore, it is imperative for individuals to time energetically costly life‐history stages (i.e. reproduction) so they overlap with seasonal peaks in food abundance and quality. Female lifetime reproductive fitness is affected by several factors that influence energy balance, including arrival date, timing of egg production, and energetic condition. Therefore, any extra energetic costs during reproduction may negatively affect timing of egg production, and ultimately a female's fitness. For example, mounting an immunological response elicits a high energetic cost, and this transfer of resources towards cell and immune system maintenance could have direct negative effects on reproductive timing. In order to determine whether an immune challenge delays onset of breeding (i.e. egg production), we administered either a humoral immune challenge (keyhole limpet hemocyanin (KLH)) (treatment) or physiological saline (control) to free‐living female dark‐eyed juncos Junco hyemalis in the period immediately prior to egg‐laying (∼4 weeks). We found that KLH‐injected females artificially delayed clutch initiation when compared to control females. These data help to refine our understanding of how free‐living birds allocate resources between reproduction and self‐maintenance processes during the critical pre‐laying period of the annual cycle.

Full lifetime perspectives on the costs and benefits of lay‐date variation in tree swallows

“…Such challenges could include enduring harsh early‐season environmental conditions such as inclement weather (e.g., Ramos et al 2002), low food availability (e.g., Young 1994, Bowlin and Winkler 2004), high levels of predation (e.g., Borgmann et al 2013), or competition for scarce nesting sites or mates (e.g., Smith 2006). Several studies of timing of breeding have explored the connection between quality and date experimentally (reviewed in Verhulst and Nilsson 2008) or by examining facets of fitness beyond reproduction (Brinkof et al 2002, Brown et al 2015, Low et al 2015, Needham et al 2017, Evans et al 2019). However, in the latter cases, breeding adults have usually been followed only to the season just after the focal breeding attempt.…”

An immune challenge of female great tits decreases offspring survival and has sex-specific effects on offspring body size

“…Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10211-020-00351-w) contains supplementary material, which is available to authorized users. Some of the avian studies that employed immune challenge showed its negative influence on clutch initiation date, egg size, brood size, brood feeding rates, chick quality, reproductive success and time to relay a replacement clutch (Ilmonen et al 2000;Råberg et al 2000;Bonneaud et al 2003;Marzal et al 2007;Gasparini et al 2009;Cucco et al 2010;Needham et al 2017). These results lend support for the costly immunity hypothesis, stating that costs of mounting an immune response are negatively reflected in current reproduction.…”