Does nest predation risk affect the frequency of extra‐pair paternity in a socially monogamous passerine?

Abstract

While considerable variations in both the frequency of extra-pair paternity (EPP) and the behavioral events that produce it are recognized among species, populations, individuals, and breeding attempts, the determinants of these variations are surprisingly difficult to establish. Nest predation may be one such determinant, since it is the most important source of reproductive failure, and past studies have suggested a variety of reproductive flexibilities under nest predation risk. However, despite its potentially significant effect on mating behaviors, nest predation risk has rarely been discussed in association with variations in intraspecific EPP patterns. Here, we examined the effect of naturally occurring nest predation, which varied between sites, years, and breeding attempts, on patterns of EPP in 92 broods (132 adults and 710 nestlings) of the Japanese great tit Parus major minor. We found that the frequency of extra-pair offspring was positively correlated with the nest predation rate, along with a correlation to breeding attempts in a season, but not with other factors such as individual quality or breeding density. Under high nest-predation risk, it may be adaptive for males to search for additional extra-pair copulation to spread the risk of losing all offspring and to invest less in mate-guarding, which also enables females to seek additional extra-mating. The results of this study suggest that nest predation risk, among other factors, may significantly influence paternity allocation in birds.

Does perceived predation risk affect patterns of extra‐pair paternity? A field experiment in a passerine bird

“…In addition, in several species, offspring from parents exposed to increased predation risk fledged at lower body mass, suggesting that parents decreased reproductive investment via reduced foraging time (Lima, ). The difference between our and previous findings (Yuta & Koizumi, ) may be related to the different types of predation pressure: increased risk of nest predation might have different effects compared to increased risk of adult predation.…”

“…There might still be a small effect on investment in extra‐pair reproduction in great tits, but if so, the sample size to detect such subtle effects may have been too low given the amount of stochastic variation in extra‐pair reproduction (Araya‐Ajoy, Kuhn, et al., ) associated to random processes in extra‐pair mating and fertilization. However, our sample size was much larger than that in the only other study of the effect of predation risk on extra‐pair reproduction; that study reported significantly higher levels of extra‐pair paternity in years and areas with a higher incidence of nest predation (Yuta & Koizumi, ). There is evidence for a variety of avian species that changes in predation risk affect reproductive investment (Lima, ).…”

Seasonal change in sexual differences in nestling size and survival: a framework to evaluate sex-dependent environmental sensitivity in the wild

“…Number of nestlings (brood size when nestlings were caught), nestling age, and maternal traits (weight, tarsus length, and wing length in each analysis) were also included as covariates. We did not include paternal traits because some nestlings were sired by extra-pair males in this population and their genetic fathers were not identified (Yuta and Koizumi 2016). Since the mean timing and length of the breeding season varied among years, we standardized the hatching date of each nest by compressing the hatching date to a range from 0 to 1 (standardized hatching date = (hatching date − earliest hatching date)/hatching date range).…”

Differences in perceived predation risk associated with variation in relative size of extra‐pair and within‐pair offspring

“…These are but two possibilities. In spite of this potential for interactions between predation risk and EPP, to our knowledge, only four studies have explicitly examined avian extra‐pair behaviour in this context, and even then, only as it relates to extra‐pair fertilization rates (Bouwman, ; Danielsen, ; Gissing, Crease, & Middleton, ; Yuta & Koizumi, ). No studies, however, have examined the relative fitness of nestlings of differing paternity status reared under experimentally heightened risk of predation.…”