Parental feeding responses to experimental short-term partner removal in a species with male and female brood desertion

Abstract

As parental care is costly, it can be expected that there will be a sexual conflict between parents over the individual levels of parental investment because each parent has limited resources to invest in a reproductive event. Theoretical models of parental investment predict that when one parent reduces its parental effort, the other parent should adjust its effort facultatively to compensate for the decrease in the mate's contribution. Here, we tested for facultative adjustments in care in the rock sparrow, Petronia petronia. In this species, both sexes can desert the brood, creating the potential for strong sexual conflict over parental care to occur. To that end, we examined how rock sparrow parents adjust their level of care in response to an experimental mate removal for a limited time period, mimicking the starting phase of the desertion process. We compared male and female provisioning rates before and after an experimental mate removal. Males behaved according to the prediction of compensatory adjustment, as they allocated more care to the offspring and returned faster to the nest after female removal, whereas females showed no response. Our study shows sexual differences in response to mate removal in a species with biparental care and strong sexual conflict over parental care, and suggests that males may use the female absence to determine their actual parental effort. Significance statement Strong differences in parental care, with one sex providing more care than the other, are widespread across the animal kingdom. Theoretical models of parental investment predict that when one parent reduces its care, the mate should adjust its care facultatively to compensate. Here, we tested for facultative adjustments in care in the rock sparrow when their mates were experimentally removed for a limited time period. We show that only male behavior was consistent with theoretical predictions as they increased their frequency of provisioning significantly after mate removal, whereas females showed no response. Our study suggests that members of a pair do not make independent decisions, but negotiate to modify their effort in direct response to the prior effort of their mate.

Females compensate for moult‐associated male nest desertion in Hooded Warblers

“…2). This plasticity in parental response has also been demonstrated experimentally in other bird species, by either shortterm mate removal (Bulla et al 2019, Cantarero et al 2019 or mate handicapping (Wright & Cuthill 1990, Sanz et al 2000. Hooded Warblers also adjust their provisioning effort to the number of nestlings, as brood size was a significant predictor of total provisioning rate, but not nestling per-capita provisioning rate (Table 1).…”

“…As the young grow older, however, and females spend less time brooding the young, deserted females are able to increase their provisioning efforts substantially, even to the point of overcompensation as the young approach fledging (Figs 1 and 2). Although we did not collect data on female brooding, other studies have noted this trade-off between provisioning and brooding for females at single-parent nests early in the nestling stage (Ezaki 1988, Wolf et al 1990, Cantarero et al 2019. In our study, however, nestling Hooded Warblers from deserted nests gained mass at the same rate as nestlings from biparental nests (Fig.…”

“…Second, the female compensatory response in provisioning nestlings is weakly, but significantly, dependent on nestling age; females tend to undercompensate for male desertion when the nestlings are young, but overcompensate when nestlings are older (Figs 1 and 2, Tables 1 and 2). The most likely explanation for this result is that deserted females with young nestlings are obliged to spend considerable time brooding and are unable to devote sufficient time to foraging to compensate fully for the absence of a feeding male (Ezaki 1988, Wolf et al 1990, Cantarero et al 2019. As the young grow older, however, and females spend less time brooding the young, deserted females are able to increase their provisioning efforts substantially, even to the point of overcompensation as the young approach fledging (Figs 1 and 2).…”

“…1990, Cantarero et al . 2019). As the young grow older, however, and females spend less time brooding the young, deserted females are able to increase their provisioning efforts substantially, even to the point of overcompensation as the young approach fledging (Figs 1 and 2).…”

“…1990, Cantarero et al . 2019). In our study, however, nestling Hooded Warblers from deserted nests gained mass at the same rate as nestlings from biparental nests (Fig.…”