Passive and active parental food allocation in a songbird

Parent-offspring conflict over food allocation can be modeled using two theoretical frameworks: passive (scramble competition) and active choice (signaling) resolution models. However, differentiating between these models empirically can be challenging. One possibility involves investigating details of decision-making by feeding parents. Different nestling traits, related to competitive prowess or signaling cryptic condition, may interact additively or non-additively as predictors of parental feeding responses. To explore this, we experimentally created even-sized, small broods of pied flycatchers and manipulated nestling cryptic quality, independently of size, by vitamin E supplementation. We explored how interactions between nestling cryptic condition, size, signals, and spatial location predicted food allocation and prey-testing by parents. Parents created the potential for spatial scramble competition between nestlings by feeding from and to a narrow range of nest locations. Heavier supplemented nestlings grew faster and were more likely to access profitable nest locations. However, the most profitable locations were not more contested, and nestling turnover did not vary in relation to spatial predictability or food supply. Postural begging was only predicted by nestling hunger and body mass, but parents did not favor heavier nestlings. This suggests that size-mediated and spatial competition in experimental broods was mild. Pied flycatcher fathers allocated food in response to nestling position and begging order, while mothers seemingly followed an active choice mechanism involving assessment of more complex traits, including postural intensity interacting with order, position, and treatment, and perhaps other stimuli when performing prey-testings. Differences in time constraints may underlie sex differences in food allocation rules.

Effects of Personality Traits on the Food-Scratching Behaviour and Food Intake of Japanese Quail (Coturnix japonica)

Simple Summary

Scratching can help animals find more buried food and thus is an important food-searching behaviour for ground-feeding birds such as gamebirds. Due to the existence of animal personality, individuals within a population may exhibit different food-scratching patterns. This study tested the impacts of personality traits (i.e., boldness and exploration) on food-scratching behaviour and food intake of Japanese quail (Coturnix japonica). We found that boldness and exploration were repeatable, respectively, and were correlated. When entering a food patch, proactive (i.e., bolder and more explorative) quails scratched for food earlier and more frequently with a longer time. Frequent and longer food-scratching may motivate longer foraging time in proactive quails which can get more food intake. The correlation between personality and food intake was sex dependent. Proactive females had more food intake during the first half of the foraging process and the correlation became weak as time went on. The pattern was opposite in males. In conclusion, our study suggests that personality traits have significant effects on animals’ food-searching strategies which may be correlated with their foraging success and fitness.

Abstract

Overall foraging success and ultimate fitness of an individual animal is highly dependent on their food-searching strategies, which are the focus of foraging theory. Considering the consistent inter-individual behavioural differences, personality may have a fundamental impact on animal food-scratching behaviour, which remains largely unknown. In this study, we aimed to investigate how personality traits (i.e., boldness and exploration) affect the food-scratching behaviour and food intake of the domestic Japanese quail Coturnix japonica during the foraging process. The quails exhibited significant repeatability in boldness and exploration, which also constituted a behavioural syndrome. More proactive, that is, bolder and more explorative, individuals scratched the ground more frequently for food and began scratching earlier in a patch. Individuals that scratched more frequently had a longer foraging time and a higher food intake. The correlation between personality traits and temporary food intake during every 2 min varied over time and was sex dependent, with females exhibiting a positive correlation during the first half of the foraging stage and males after the initial stage. These findings suggest that personality traits affect the food-scratching behaviour and, thus, the food intake of quails. Our study provides insights into the impact of personality traits on animal’s foraging behaviour by influencing their food-searching strategies.

Sex-dependent risk-taking behaviour towards different predatory stimuli in the collared flycatcher

Prey animals may react differently to predators, which can thus raise plasticity in risk-taking behaviour. We assessed the behavioural responses of nestling-feeding collared flycatcher (Ficedula albicollis) parents towards different avian predator species (Eurasian sparrowhawk, long-eared owl) and a non-threatening songbird (song thrush) by measuring the latency to resume feeding activity. We found that the sexes differed in their responses towards the different stimuli, as males resumed nestling-provisioning sooner after the songbird than after the predator stimuli, while latency of females was not affected by the type of stimulus. Parents breeding later in the season took less risk than early breeders, and mean response also varied across the study years. We detected a considerable repeatability at the within-brood level across stimuli, and a correlation between the latency of parents attending the same nest, implying that they may adjust similarly their risk-taking behaviour to the brood value. Repeated measurements at the same brood suggested that risk-taking behaviour of flycatcher parents is a plastic trait, and sex-specific effects might be the result of sex-specific adjustments of behaviour to the perceived environmental challenge as exerted by different predators. Furthermore, the nest-specific effects highlighted that environmental effects can render consistently similar responses between the parents.

Urban resources limit pair coordination over offspring provisioning

The amount of care parents provide to the offspring is complicated by an evolutionary conflict of interest (‘sexual conflict’) between the two parents. Recent theoretical models suggest that pair coordination of the provisioning may reduce this conflict and increase parent and offspring fitness. Despite empirical studies showing that pair coordination is common in avian species, it remains unclear how environmental and ecological conditions might promote or limit the ability of parents to coordinate care. We compared the level of pair coordination, measured as alternation and synchrony of the nest visits, of house wrens Troglodytes aedon pairs breeding in a rural (10 nests) and a suburban (9 nests) site and investigated how differences in parental behaviours were related to habitat composition, prey abundance and how they ultimately related to reproductive success. We found that parents alternated and synchronized their nest visits more in the rural site compared to the suburban one. The suburban site is characterized by a more fragmented habitat with more coniferous trees and less caterpillar availability. Offspring from the rural site were heavier at fledging than at the suburban site. Taken together, these results suggest that environmental conditions play an important role on the emergence of coordinated parental care and that considering environmental variables is pivotal to assess the fitness consequences of parental strategies.

Manipulation of parental effort affects plumage bacterial load in a wild passerine

It has been suggested that plumage microorganisms play an important role in shaping the life histories of wild birds. Some bacteria may act as pathogens or cause damage to feathers, and thereby reduce individual fitness. Intense parental care in birds can result in a reduction of self-maintenance and preening behavior in parents and therefore might affect the dynamics of microbiota living on their feathers. However, experimental evidence of this relationship is virtually absent. We manipulated the parental effort of wild breeding pied flycatcher (Ficedula hypoleuca) females by modifying their brood size or temporarily removing male partners. We expected that experimentally decreasing or increasing parental effort would affect feather sanitation in females and therefore also bacterial density on their plumage. In accordance with this hypothesis, manipulation affected the density of free-living bacteria: females with reduced broods had the lowest number of free-living bacteria on their feathers, while females left without male partners had the highest. However, manipulation did not have a significant effect on the densities of attached bacteria. Our results provide experimental evidence that a trade-off between self-maintenance and parental effort affects plumage bacterial densities in birds.