Cascading costs of reproduction in female house wrens induced to lay larger clutches

Abstract

In many species, females produce fewer offspring than they are capable of rearing, possibly because increases in current reproductive effort come at the expense of a female’s own survival and future reproduction. To test this, we induced female house wrens (Troglodytes aedon) to lay more eggs than they normally would and assessed the potential costs of increasing cumulative investment in the three main components of the avian breeding cycle – egg laying, incubation, and nestling provisioning. Females with increased clutch sizes reared more offspring in the first brood than controls, but fledged a lower proportion of nestlings. Moreover, nestlings of experimental females were lighter than those of control females as brood size and pre-fledging mass were negatively correlated. In second broods of the season, when females were not manipulated, experimental females laid the same number of eggs as controls, but experienced an intra-seasonal cost through reduced hatchling survival and a lower number of young fledged. Offspring of control and experimental females were equally likely to recruit to the breeding population, although control females produced more recruits per egg laid. The reproductive success of recruits from broods of experimental and control females did not differ. The manipulation also induced inter-seasonal costs to future reproduction, as experimental females had lower fecundity than controls when breeding at least two years after having their reproductive effort experimentally increased. Finally, females producing the modal clutch size of seven eggs in their first broods had the highest lifetime number of fledglings.

Cumulative reproductive costs on current reproduction in a wild polytocous mammal

“…Positive associations between previous and current litter size are likely due to persistent individual differences in state, involving differences in resource acquisition and allocation (McNamara & Houston, 1996;van Noordwijk & de Jong, 1986), which determine reproductive success. This is supported by results from a previous study in yellow-bellied marmots, which found a positive effect of previous year reproduction on current reproduction probability (Nuckolls, 2010), and by studies in other systems (e.g., Alpine chamois, Rupicapra rupicapra, Tettamanti, Grignolio, Filli, Apollonio, & Bize, 2015; wood ducks, Aix sposa, Kennamer, Hepp, & Alexander, 2016 (Fite et al, 2005), and thus costs could also be transferred from mother to offspring (Martin & Festa-Bianchet 2010;Hodges, Bowers, Thompson, & Sakaluk, 2015). In female house mice (Mus musculus), for example, offspring in larger litters had lower weaning weights that offspring from smaller litters (König, Riester, & Markl, 1988 Morris, 1992).…”

“…However, our results do not support this expectation: generally, individuals appear to have either intermediate or low values for both cumulative reproductive measures, and individuals that reproduce often but wean small litters (high‐low) or reproduce less often but wean larger litters (low‐high) have higher current reproduction probabilities than either of the other two groups (i.e., high‐high or low‐low). Mothers can reduce allocation to their young through decreased milk production (Fite et al, ), and thus costs could also be transferred from mother to offspring (Martin & Festa‐Bianchet ; Hodges, Bowers, Thompson, & Sakaluk, ). In female house mice ( Mus musculus ), for example, offspring in larger litters had lower weaning weights that offspring from smaller litters (König, Riester, & Markl, ).…”

Maternal Natal Environment and Breeding Territory Predict the Condition and Sex Ratio of Offspring

“…We also found increasing brood sizes to be associated with an increased probability that a female would return to breed in the study population in the future, an apparently paradoxical result if increased reproductive effort imposes costs to a female’s long-term survival and future reproduction (Williams 1966; Gustafsson and Sutherland 1988; Hodges et al 2015). However, a number of hypotheses may explain this result, even if reproduction is generally costly.…”

Spatial and temporal variation in breeding parameters of two south‐temperate populations of House Wrens

“…Some investigators have proposed that multibrooded birds should breed as early as ambient conditions permit, maximizing the number of annual breeding attempts rather than clutch size (Lack , García‐Navas and Sanz , Dunn and Møller ). Therefore, under certain circumstances, producing more broods with fewer nestlings per brood may improve lifetime reproductive success (Hodges et al ). For south‐temperate House Wrens, the probability of second nesting attempts increases with early laying dates of first nesting attempts, and pairs that produce two broods fledge more nestlings per breeding season than pairs that produce a single brood (Carro et al ).…”