Search

Animals living near urban habitats face many pressures linked with human disturbance. While individuals vary in their ability to cope with disturbance, it is predicted that individuals in highly disturbed environments will be bolder and more aggressive than those in less disturbed environments. Using little penguins, Eudyptula minor, we investigated whether individual aggressiveness was consistent across trials and whether aggressiveness was greater in colonies that experience higher levels of unregulated human disturbance. We scored aggressiveness at the nest, based on the penguins’ response to a standardized nest intrusion experiment, across four penguin colonies in South Australia. Nest defence scores were significantly repeatable over two trials, suggesting that it was a good indicator of personality in little penguins. Island was a significant predictor of nest defence score, with little penguins on Granite Island (the island with the greatest amount of unregulated human disturbance) being more aggressive than those on Troubridge Island (the island with the lowest amount of human disturbance). Considering that humans increasingly interact with animals, whether directly or indirectly, understanding the mechanisms behind nonrandom distribution of behaviours may have important implications for population management and conservation.

Foraging site selection and site fidelity can have implications for many ecological processes. The degree of site fidelity differs greatly not just between species but also within populations. Some of this variation may be explained by a win-stay–lose-shift (WSLS) strategy, where an individual returns to its most recent foraging area only if the previous visit was profitable. However, the use and adaptive value of this strategy have mostly been tested in captivity, largely because of the difficulty in obtaining accurate measures of profitability (foraging efficiency) in the wild. Here, we used a rare combination of data on movements of breeding black-browed albatrosses, Thalassarche melanophris, tracked using satellite transmitters, and on chick meal mass obtained from automatic nest balances, to test whether individuals adopted a WSLS strategy, and how this strategy performed in terms of provisioning rate. We found results consistent with the use of a WSLS strategy, and that the strategy had some adaptive value, albeit rather limited. Our observational study of free-living seabirds corroborates previous experimental results suggesting that animals account for recent foraging success in their decision making and can adapt their strategy to local resource dynamics.

Leaving the nest is a key transition in the life of altricial birds, whereby fledging decisions should depend on multiple factors, including the risk of predation. High postfledging predation risk may favour fledging at a more advanced stage of development, if more developed fledglings are better at escaping predation, or together with others. While comparative studies have highlighted the role of predation risk for between-species variation in the timing of fledging, drivers of within-species variation in fledging behaviour remain largely unknown. We presented owl models near blue tit, Cyanistes caeruleus, nests during the first half of the day throughout the fledging period to simulate an increased risk of postfledging predation. Using an automated monitoring system, we then recorded the precise fledging times of 595 nestlings from 105 nests (52 predator-treated, 53 control nests). Contrary to our predictions, the predator presentations did not affect the age at which nestlings fledged, the time of day of fledging or other aspects of fledging behaviour. The tendency to fledge together with siblings was affected, but the effect was in the opposite direction to that expected, with nestlings exposed to the predator treatment being more likely to fledge alone. Parents visited predator-treated nests less often, but this effect diminished over the course of the morning. We suggest several explanations for why the behavioural responses to the predation risk manipulation were generally limited.

The transition from nestling to fledgling is a key moment in the development of altricial birds. Mortality immediately after fledging is typically high and selection should favour fledging strategies that maximize the chance of survival. While several studies have examined the influence of ecological conditions or nestling development on the timing of fledging, the question whether nestlings influence each other's behaviour has received little attention. We tested how fledging decisions of blue tit, Cyanistes caeruleus, nestlings depend on the behaviour of their nestmates. First, we show that in unmanipulated broods, fledging events within a nest were highly clustered and nestlings fledged closer in time to a sibling than expected if fledging events were independent of one another. We then experimentally tested whether nestlings adjust their timing of nest departure to the behaviour of their nestmates, by translocating nestlings to a brood that differed in age by 2 days. Nestlings that were 2 days younger than their adoptive brood advanced their fledging time such that they fledged close in time to a nestmate. Nestlings that were 2 days older than their adoptive brood significantly delayed their fledging time, but they were often the first to fledge and were not always followed close in time by a nestmate. We conclude that nestling blue tits have a strong propensity to leave the nest close in time to nestmates. The adaptive significance of this behaviour warrants further study.

When selecting a breeding site, individuals can use social information to reduce the uncertainty regarding habitat quality. Individuals of several bird species tend to reuse nests previously occupied by conspecific or heterospecific competitors but the proximate mechanisms underlying this behaviour remain unclear. Reoccupying nests previously used by competitors could result from individuals copying competitors' choices (the ‘social information’ hypothesis). Alternatively, it could allow individuals to fulfil their need for a soft nest substrate (e.g. by improving thermal insulation or reducing egg breakage risks) at low costs, regardless of previous occupancy (the ‘comfort’ hypothesis). Here, we aimed to determine which of these nonmutually exclusive mechanisms triggered the preference for old conspecific nest material in a secondary cavity-nesting raptor that does not add lining material to its nests, the lesser kestrel, Falco naumanni. Using an experimental design forcing settling lesser kestrels to choose between two adjacent nestboxes containing different substrates, we detected a strong preference for soft substrates (peat moss or old conspecific or European roller, Coracias garrulus, nest material) over coarse mineral substrate, especially when the soft substrate also provided social information about previous nest use by a competitor. Despite the apparent absence of preference when directly comparing settlement patterns in soft substrates with and without social information, early settling individuals favoured the substrate with social information, while late settling ones favoured the substrate without social information. This could reflect intraspecific competition avoidance by late arriving individuals that may be competitively inferior to early arriving ones. This hypothesis is supported by a later laying date of young breeders in our population. Our findings suggest that both comfort seeking and social information use explain the preference for previously used nest cavities, and that nest site choices may depend on individual competitive abilities and experience.

Urban animals often show bolder behaviour towards humans than their nonurban conspecifics. However, it is unclear to what extent this difference is due to consistent individual characteristics or to plasticity such as habituation. To address this question, we investigated parental risk-taking behaviour in 371 female great tits in urban and forest populations by checking their nest repeatedly (several times per week, for up to nine breeding episodes) and recording their behavioural responses to this recurring disturbance during incubation. We found that urban females were bolder, as they stayed on the nest more often than females in forests. Furthermore, great tits produced alarm calls around the nests more frequently in urban than in forest habitats. There was no habitat difference in the frequency of an antipredator behaviour, the hissing threat display on the nest, although this was rare in both habitats. We also tested the consistency and plasticity of risk-taking behaviour on three different temporal scales (within breeding attempts, between broods within a year and across years). Staying on the nest was highly repeatable within females, whereas alarm calls had low repeatability within pairs at all three temporal scales. The probability of staying on the nest increased within breeding attempts, whereas the probability of alarm calls increased across years. Neither consistency nor plasticity in these components of risk taking differed between urban and forest habitats. We conclude that urban birds are bolder in multiple behavioural measures and, overall, both stable individual differences and behavioural plasticity may have contributed to the higher risk taking we often see in urban populations. Furthermore, staying on the nest appears to be an individually consistent trait in female great tits regardless of habitat urbanization, providing a low-impact measurement of risk taking, which may potentially facilitate field studies related to individual differences in behaviour.

Animal architecture is diverse in form and structure, and extraordinarily intricate, often facilitated by the collective behaviour of several individuals. Social spider webs are one such example of animal architecture, robustly supporting the collective colony weight and intercepting prey for the entire colony. Thus, these webs are interesting, yet little studied from architectural and behavioural perspectives. In the social spider Stegodyphus sarasinorum we examined the spatiotemporal dynamics of web architecture and tracked web development in different group sizes through controlled experiments and image analysis. Geometrical parameters including coordination number, and pore size remained constant across group sizes. Silk density was highest near the retreat (nest) and decreased with radial distance for all group sizes. We tested the silk conservation hypothesis, a proposed benefit for the evolution of group living, by asking whether (1) total silk investment increases with group size and (2) per capita silk investment decreases with group size. Our results indicate that while larger colonies produced more silk than smaller ones, per capita silk investment did not decline in larger groups. We propose further investigations into the roles of ecological factors and body condition in shaping individuals’ silk investment with consequences for web architecture and colony fitness.

Animals create diverse structures, both individually and cooperatively, using materials from their environment. One striking example are the nests birds build for reproduction, which protect the offspring from external stressors such as predators and temperature, promoting reproductive success. To construct a nest successfully, birds need to make various decisions, for example regarding the nest material and their time budgets. To date, research has focused mainly on species where one sex is primarily responsible for building the nest. In contrast, the cooperative strategies of monogamous species in which both sexes contribute to nest building are poorly understood. Here we investigated the role of both sexes in nest building and fitness correlates of behaviour in wild, monogamous jackdaw pairs (Corvus monedula). We show that both partners contributed to nest building and behaved similarly, with females and males present in the nest box for a comparable duration and transporting material to the nest equally often. However, while females spent more time constructing the nest, males tended to invest more time in vigilance, potentially as a means of coping with competition for nest cavities. These findings suggest a moderate degree of division of labour, which may facilitate cooperation. Moreover, some aspects of behaviour were related to proxies of reproductive success (lay date and egg volume). Females that contributed relatively more to bringing material laid earlier clutches and pairs that spent less time together in the nest box had larger eggs. Thus, selection pressures may act on how nest building pairs spend their time and cooperatively divide the labour. We conclude that cooperative nest building in birds could be associated with monogamy and obligate biparental care, and provides a vital but relatively untapped context through which to study the evolution of cooperation.HighlightsIn wild monogamous jackdaws, mates behaved similarly and cooperated to build their nest.Females built more and called more frequently; males tended to be more vigilant.Females that contributed relatively more to transporting nest material laid earlier clutches.Pairs that spent more time together in the nest box had smaller eggs.Cooperation may be crucial in light of obligate biparental care and nest site competition.

Synchronous digging activity and emergence from underground nests is important for sea turtle hatchlings, as it reduces predation risk and decreases energy consumption. However, patterns of underground hatching and diel digging activity prior to emergence are invisible and remain largely unknown. In this study, we acoustically monitored the activity of green turtle, Chelonia mydas, hatchlings from hatching to emergence in the field and laboratory. During the hatching period, we did not observe characteristic acoustic events corresponding to pipping and hatching. Hatchlings started digging even though there were still unhatched eggs above them, indicating that green turtles did not hatch as one synchronous group. This observation did not support our hypothesis that synchronized hatching facilitates synchronous emergence. Digging activity tended to increase at night as the hatchlings approached the sand surface and nest emergence became imminent. It is not surprising that there was diel variation in digging activity as the hatchlings approached the surface because diel fluctuations in sand temperature can provide a diel cue. Surprisingly, a diel change in digging activity was also observed when hatchlings were still at a sand depth where temperature remained relatively constant throughout the day (that is, a few days before emergence) and in the laboratory at a constant temperature. This study suggests that the diel activity pattern of hatchling green turtles may occur even in the absence of a diel temperature fluctuation cue.

In many animal systems, the defence of a territory or nest coincides with the defence of offspring, and it is often unclear whether the defence behaviour exists for the purpose of offspring protection, territory protection or a combination of both. In species with biparental care, the drivers of defence behaviours in males may differ from those in females, particularly if there are sex-specific fitness benefits from the current brood or territory. In this study, we present field experiments aimed at elucidating sex differences in the drivers behind nest defence in a fish species (Variabilichromis moorii, Cichlidae) with biparental care. High rates of cuckoldry in this species create asymmetries in brood value between mates, suggesting that increased brood survival may be a weaker driver of male than of female defence effort. We conducted parent and offspring removal experiments and found that following the removal of their mates, single males lost significantly more fry than single females. Some single males lost their territories, while others constricted their space use, suggesting that experimental divorce decreased their success in territory defence. Removal of fry from territories guarded by both parents caused the defence behaviour to become more male biased, that is, males contributed relatively more to defence without any fry present. Our results suggest that, relative to that of females, male defence behaviour is more strongly driven by territory retention than by brood protection. Nevertheless, the presence of males improves parents’ abilities to keep territory intruders at bay, and thus probably confers benefits to broods. We conclude that the drivers of defence behaviours differ between the sexes in this species, with defence behaviours aligning well with the traditional definition of parental care for females, but less so for males. published

Egg rejection behaviour is a host strategy adopted by birds against brood parasitism. The optimal acceptance threshold hypothesis predicts that, when the frequency or risk of parasitism increases, host acceptance thresholds should become more restrictive. Here, we investigated egg rejection behaviour in the Daurian redstart, a cavity-nesting host of the common cuckoo, Cuculus canorus. In a Daurian redstart population located in the northern cold-temperate zone of China where redstarts have two peaks of egg laying during the breeding season, cuckoos can only parasitize redstart nests during the second egg-laying peak due to their late arrival on the breeding grounds. We artificially simulated brood parasitism by introducing a model cuckoo egg into a redstart nest during both egg-laying peaks to test the prediction that redstarts should reject eggs at a greater rate during the second than the first egg-laying peak. In accordance with the optimal acceptance threshold hypothesis, Daurian redstarts showed significantly higher egg rejection rates during the second egg-laying peak. This result indicates that temporal variation in egg rejection behaviour by Daurian redstarts may be an adaptive response to seasonal change in risk of cuckoo parasitism. To our knowledge, this is the first study showing that the egg rejection rate of a host population increases with increasing risk of cuckoo parasitism within a breeding seas.

In altricial birds, leaving the nest is a key life history transition associated with a high risk of mortality. Studies of numerous species have shown that young typically fledge early in the day, and it is often asserted that early fledging is important for survival; however, evidence for this hypothesis is limited. We used an automated monitoring system to obtain precise fledging times of 1582 young blue tits, Cyanistes caeruleus, from 230 nests. As expected, nestlings primarily fledged early in the day (84% fledged before midday). However, we found no evidence that early fledging was associated with higher postfledging survival (i.e. recorded the following autumn or later). We propose two alternative explanations for the morning peak in fledging. Hypothesis 1 is that some offspring reach a developmental threshold for fledging overnight and leave the nest early the next day. This is supported by our observation that offspring that fledged early in the day tended to be more developed than those that fledged later in the day, that is, they were older and had a high body mass (measured at 14 days of age) for their fledging age. Hypothesis 2 is that the timing of fledging is related to parental provisioning behaviour. Our results do not support this hypothesis. Parents reduced their nest visit rate over the course of the day, but offspring did not fledge earlier when their parents decreased their visit rate more strongly with time of day. In conclusion, our results do not support the notion that the time of fledging affects survival but suggest a link with nestling development.

Coevolutionary arms races between brood parasites and hosts can evolve along several distinct trajectories. To understand why, host–parasite interactions must be examined at every stage of the breeding cycle. While there have been numerous studies of interactions at the egg and nestling stages, studies of preparasitism ‘frontline’ interactions have received less attention. Frontline defences in hosts should be widespread, both because they can preserve the entire host clutch (while postparasitism defences, such as egg or chick rejection, do not) and because they tend to overlap with defences against nest predation. We investigated whether parasitism by the little bronze-cuckoo, Chalcites minutillus, has selected for frontline defences in large-billed gerygones, Gerygone magnirostris, a host that rejects cuckoo chicks. We considered three possible defences: (1) mobbing of adult cuckoos near the nest, (2) ‘decoy nest clustering’ of active nests alongside old nests and flood debris, and (3) cryptic nest architecture. Gerygones were more likely to mob a mount of a cuckoo near the nest than that of a hawk or harmless sympatric passerine. The role of nest traits in repelling parasitism was equivocal; gerygones built their nests alongside previously used nests more often than expected by chance. The experimental addition of decoy nests did not reduce parasitism rates but did lead to a significant delay in latency to predation. Although large-billed gerygones build large nests compared to other gerygones species, we found that larger nests were more likely to be parasitized than smaller nests. We conclude that parasitism has selected for a portfolio of defences in large-billed gerygones, comprising both low-cost, but mostly ineffective, frontline defences (mobbing, some nest traits), and a high-cost, but highly effective, chick stage defence (chick rejection). Thus, the relatively low effectiveness of frontline and egg stage defences may explain why some hosts evolve the rare defence of chick rejection.

The sublethal effects of infectious disease on reproductive behaviour and mating success are not well understood. Here, we investigated predictors of male mating success in one of Australia's most critically endangered vertebrates: the northern corroboree frog, Pseudophryne pengilleyi. Using a genomic approach to assign parentage, we explored whether infection with the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), a pathogen responsible for amphibian declines globally, influenced male calling behaviour and mating success. We also explored whether male mating success was predicted by phenotypic traits (age, body size, coloration, call characters) that potentially signal genetic quality, and the soil moisture (water potential) of male-constructed terrestrial nests, which may directly impact offspring survival. We found that Bd significantly influenced male advertisement; Bd-infected males produced calls with significantly higher pulse repetition rates than uninfected males. Older males had a higher probability of mating; however, variation in the number of eggs in a nest was most strongly explained by an interaction between male Bd infection status and call pulse repetition rate. We propose that these relationships may result from either pathogen-mediated changes to host behaviour or host-mediated changes to behaviour (e.g. terminal investment). Regardless of the mechanism, this is the first evidence that male mating success in an amphibian can be influenced by male Bd infection status, highlighting a novel mechanism through which this virulent pathogen can affect amphibian fitness. More broadly, these findings add to a growing body of evidence that pathogens can alter the reproductive biology of their hosts. From a conservation perspective, increased consideration of how sexual selection operates in altered environments has the potential to assist with the management of threatened amphibians worldwide.

Individuals and social groups balance foraging activities with other energetically demanding behaviours. In honey bee colonies, foraging and nest defence behaviours are performed by similar-aged bees, and so hives must adjust their workforce investment to fulfil both tasks. We investigate this balance in the context of honey robbing, a tactic in which foragers invade a victim hive, kill worker bees and steal honey stores. Robbing is highly beneficial because stored honey is a plentiful, concentrated food resource. However, robbing requires a large workforce to overwhelm the defences of the victim hive; it is unknown how robbing hives adjust other behaviours to accommodate this demand. We developed a method to provoke a hive to engage in simulated robbing and measured rapid changes in foraging activity and nest defence. Surprisingly, robbing hives increased both behaviours. Guards, the individuals responsible for nest defence, specifically increased defensiveness towards their own nestmates as they returned from a robbing trip. We found that increased foraging activity and changes in forager odour profiles from prolonged exposure to victim hive honeycomb were insufficient to explain robbing-induced changes in guard defensiveness. However, brain gene expression profiles of robbing foragers suggest these bees are unusually aggressive, and thus more likely to provoke aggression from nestmate guards. Increased forager aggression occurred even in the absence of direct competition with victim bees. Thus, although increased guard defensiveness may be costly in terms of increased nestmate mortality, because the ecological conditions that promote robbing simultaneously increase the likelihood a hive will become a robbing target, guards may use cues from returning nestmates to determine invasion risk and adjust their defensiveness accordingly. These results suggest that colonies use social information to dynamically optimize both foraging and defensiveness in order to maximize the benefits and minimize the costs of this high-risk tactic.

Behaviours whose primary function is not signalling can convey information that other individuals can use to make relevant decisions. In cooperatively breeding vertebrates, feeding young that are not own offspring typically provides indirect fitness payoffs, but group members may also benefit directly by advertising their contribution to their social mates, to either increase their ‘social prestige’ or obtain a share of territory commodities (‘pay to stay’). Evidence of such a signalling component of brood provisioning, however, remains controversial. In the cooperative society of carrion crows, Corvus corone, male subordinates have little chance of independent reproduction and do the best of a bad job by helping to raise the current brood. The value of future reproduction is instead higher for subordinate females, which, because they have better prospects of finding a breeding vacancy, generally invest less than males in helping at the nest. Under these circumstances, dominants are expected to be more vigilant over the contribution to brood provisioning by female subordinates, which in turn, might need to show their helpfulness to retain group membership. In accordance with this idea, we found that female retained offspring increased the ‘visibility’ of their contribution by provisioning in front of the dominant breeders significantly more than any other category of group members. In addition, retention of group membership for female offspring was associated with their perceived effort in chick feeding. Our results are consistent with the hypothesis of ‘pay to stay’ and suggest that a signalling component of helping can arise in a ‘typical’ kin-based cooperative society.

Associations between parasite loads and sexual signal expression have long been the focus of research. However, our understanding of how sexual selection operates in the context of multiple parasite infections within the same host is still quite limited. We examined the expression of plumage coloration, which is sexually selected in North American barn swallows, Hirundo rustica erythrogaster, and tail streamer length, which is sexually selected in other barn swallow subspecies, in the context of eight different parasite infections. We found that two parasites, nest mites and Plasmodium, were associated with colour expression, but in opposite directions. Attractive males were less likely to have mites in their nests, but more likely to be infected with Plasmodium. We found that different underlying mechanisms were generating the links between these different parasites and the same colour signal. Males that invested more in colour expression were less likely to survive when infected with Plasmodium, suggesting a physiological mechanism linking colour to Plasmodium infections. However, we found no clear cost to males when examining nest mites, which primarily infect offspring. Instead, using experimental mite manipulations, we provide evidence for a behavioural mechanism, where territorial behaviour and male–male competition likely drive the association between colour expression and nest mite infections. We did not find associations between parasites and streamer length in this subspecies, suggesting that the links between divergent sexual signals and parasites may be quite flexible. These results suggest that the evolution of a single sexual signal can be shaped by several, even opposing, links with different parasite infections.

Climate-mediated phenological shifts can cause species to lose access to their primary prey while increasing opportunities for alternative-prey encounters. Species that are able to capitalize on alternative resources could potentially profit from prey-switching should the benefits of procuring these alternative resources outweigh their acquisition costs. Polar bears, Ursus maritimus, use sea ice as a platform to hunt seals, and individuals inhabiting the southern-most extent of their range rely on accumulated fat reserves to sustain themselves during the increasingly lengthy ice-free season. In response to declining access to their primary prey through documented sea ice loss, some polar bears are foraging on the eggs of birds in lieu of hunting opportunities on ice, as their onshore arrival is increasingly overlapping with birds’ breeding schedules. To gain a better understanding of the energetic consequences of this behaviour, we used aerial drones to record polar bears foraging on sea duck eggs (common eider, Somateria mollissima) on Mitivik Island, Nunavut, Canada. Using these data, we examined variation in individual polar bear foraging behaviours and estimated the energetic benefits and costs associated with foraging on common eider eggs. Because of low costs associated with nest searching and consumption, the energetic cost of foraging remained relatively constant throughout the 2-week observation period. However, we found that as the common eider breeding season progressed, polar bears consumed eggs at a lower rate as they depleted the nesting colony and spent proportionally more time searching for nests. Collectively, this foraging pattern led to an overall declining trend in the net energy gained from egg consumption. Foraging on common eider eggs during increasingly lengthy ice-free seasons is apparently beneficial for polar bears, but only during a limited window of opportunity. By coupling energetic estimates with detailed behavioural data collected through aerial videography, this study provides a quantification of both the benefits and costs of egg consumption for polar bears.

The reciprocal pilferage hypothesis argues that, despite the occurrence of pilferage, scatter-hoarding behaviour could evolve if cache loss is compensated by gains pilfered from others. However, this model has not been strictly tested because of the difficulty associated with tracking caches, including ownership, over long periods. Using infrared radiation cameras, we tracked caching of Juglans regia seeds by groups of two Pere David's rock squirrels, Sciurotamias davidianus, within a large natural enclosure. Our goal was to quantify how squirrels responded to the presence of a conspecific when seed hoarding and pilfering and test the reciprocal pilferage hypothesis. We found that the numbers of seeds harvested from the seed sources and pilfered from conspecifics was initially low, increasing as seeds were removed and then dropping off once few seeds remained at the seed sources. Additionally, the number of seeds scatter hoarded increased with a decreasing number of seeds remaining at the sources. Seeds harvested from the source and pilfered from competitors were at first cached randomly within the enclosure and then centralized to the low-competition area near the nest as seed sources declined. Overall, pilferage was not high. The proportions of seeds pilfered did not vary between conspecifics and were positively correlated with each other over trials. More seeds were harvested from the seed sources than pilfered by competitors at the early stage of hoarding. These results suggest that, under conspecific competition, squirrels appeared first to compete for food at the sources, then for caches with each other as food sources decreased, and finally cache ownership became relatively stable. Squirrels compensated for cache loss by both harvesting food from the sources and pilfering caches from its competitor. The amount of seeds gained from pilfering was sufficient to replace pilfered caches, supporting the reciprocal pilferage hypothesis.

Cryptic interactions among individuals in animal societies can be challenging to detect due to their rarity or their covert nature, but they can have important fitness consequences for the individuals involved. Using radiofrequency identification (RFID) technology, we examined the pattern and function of visits to the nests of conspecifics in western bluebirds, Sialia mexicana. Western bluebirds live in kin neighbourhoods year-round and exhibit a low frequency of cooperative breeding. Various functions have been proposed for extraterritorial visits, but few studies explore multiple potential functions. We asked whether extraterritorial visits in western bluebirds are consistent with (1) seeking extrapair copulations (EPCs), (2) prospecting for future nest sites or mates and/or (3) maintaining relationships with kin. We found some evidence supporting all three functions of visits. Postdawn visits made by males to unrelated females were significantly more likely to occur during the period in which males seek within-pair matings than outside this period. We found that visiting a given nestbox or a given potential mate was associated with an increased probability of nesting in that box or with the potential mate the subsequent year, suggesting that some visits are linked to prospecting. Finally, males preferentially visited kin: the proportion of visits to relatives was greater than the expected mean proportion of visits if males visited boxes randomly while travelling the same distance. Our work supports multiple functions of extraterritorial visits and highlights the importance of rare and cryptic behaviours to understanding social behaviour.

In resource defence mating systems where males control nest sites, complex interrelationships between nest characteristics and nest advertisement are likely to influence female mate choice. Surprisingly, however, we know little about the influence of such relationships on female mating decisions. In terrestrial-breeding oviparous species, one character likely to have a major influence on female nest site selection is nest moisture. In addition to influencing the susceptibility of eggs to desiccation, nest moisture also stands to influence nest pH and offspring fitness, as well as the hydration state of resident males, and their potential to advertise. Together, such interrelationships could strongly influence female mating decisions. The aim of this study was to use a long-term field study combined with a multivariate approach to investigate the combined influence of nest moisture, nest pH and male acoustic advertisement on female nest site selection in a wild population of red-backed toadlets, Pseudophryne coriacea. We found that females deposited more eggs in wetter and less acidic nests, and that these variables were positively correlated. Moreover, nest moisture and pH in combination were positively related to the calling potential of resident males, and nests that were advertised more often received more eggs. These results suggest that nest site selection in red-backed toadlets is influenced by a complex interplay between covarying nest characteristics that together influence male sexual signalling and nest advertisement. More broadly our findings highlight the potential for nesting behaviour to be mechanistically intertwined with mate choice.

Insect societies are challenged by harmful pathogens that originate from waste, such as faeces, food leftovers or corpses. The discarding of waste to outside the nest reduces these sanitary risks and contributes to the social immunity of ant colonies. In this study, we tested whether the nest-cleaning behaviour in Myrmica rubra colonies differed depending on the pathogenicity of waste or the presence of brood as well as over successive exposure to waste. We introduced waste items covered with entomopathogenic Metarhizium brunneum conidia and items without conidia in either broodright or broodless colonies. The greater the pathogenicity of waste, the faster it was discarded by the ants, although this did not prevent higher mortality rates in workers and larvae. When exposed a second time to waste items, ant colonies improved the discarding of nonpathogenic waste but became less efficient at removing infected waste, probably due to morbidity in the workers’ population. Most surprisingly, we found that the presence of brood enhanced the hygienic responses of workers, with ant colonies doubling their probability of discarding waste items to outside the nest. Overall, we show that ants can detect entomopathogenic conidia on waste and take steps accordingly to hasten the removal of infected items. Furthermore, we demonstrate the upregulating role of larvae which results in enhanced performance of hygienic tasks and reinforces sanitary control inside the colony.

Research into plumage ornaments and plumage signals of individual state has focused primarily on males, while variation among females has received far less attention. White patches of plumage around the eye (eye patches) are a female-specific plumage trait in the wood duck, Aix sponsa, a sexually dimorphic species of cavity-nesting waterfowl in North America. We observed considerable variation in the size of these patches among females and sought to evaluate whether this trait might indicate individual quality (‘quality cost hypothesis’) or the influence of stress or past investment (‘stress indicator hypothesis’). We measured the area of female eye patches in five populations of wood ducks during three breeding seasons and examined whether eye patch area varied in relation to age, nest success, future breeding, activity and/or body condition. Eye patch area was highly variable among individuals but repeatable within individuals, varied across years and study sites, correlated strongly with age but weakly with an index of body condition. For individuals greater than 4 years of age, eye patch area was negatively related to the likelihood of returning to breed in the following year. Eye patch size was positively correlated with nest initiation date and this was more pronounced in older birds, but there was no correlation of eye patch area with clutch size or hatch success. Our results suggest that this unique female-specific plumage trait reflects individual age and future reproduction potential. Larger eye patches in older females may be an indicator of senescence or terminal investment, and we hypothesize that eye patch size could act as a signal of individual state or social status in this species.

Avian brood parasites lay their eggs in the nests of other species, leaving the hosts to care for the parasitic offspring. The bookkeeping hypothesis predicts that, in order to reduce competition between parasitic nestlings, female parasites should keep a mental inventory of host nests that they have already parasitized and avoid laying multiple eggs in the same host nest. However, selection against repeat parasitism should be weaker when host nests are limited, or when hosts are able to rear more than one parasitic nestling. Here we use microsatellite genotyping of parasitic eggs to test whether female screaming cowbirds, Molothrus rufoaxillaris, avoid repeatedly parasitizing nests of their primary host, the greyish baywing, Agelaioides badius, in Argentina. Parasitism rates were extremely high (96.5% of 57 host clutches were parasitized with an average of 5.7 cowbird eggs each), indicating that host nests are limited. Although eggs laid by the same female showed moderate spatiotemporal clustering, individual females rarely laid more than one egg in the same host clutch (2 of 57 clutches, 26 of which contained multiple genotyped cowbird eggs). Females were much more likely to lay subsequent eggs in different host nests than to return to the same host nest. We found no evidence for kin structure among female cowbirds parasitizing the same host nest, which were no more closely related than chance would predict. These results suggest that female screaming cowbirds frequently lay eggs in host nests that have already been parasitized by unrelated females. However, they typically lay just one egg per host clutch, even though greyish baywings are capable of rearing several nestlings. Since screaming cowbird laying is often poorly synchronized with that of their host, avoidance of repeat parasitism may be adaptive if it allows females to spread the risk of failure among multiple host nests.

In many brood-rearing species, suitable nesting resources are needed for nest construction. Here, we used males of a small marine fish, the sand goby, Pomatoschistus minutus, to study the associations between the nest owner's phenotype (i.e. body size), the characteristics of the nesting resource used for nest construction (i.e. resource size and shape) and nest-building behaviour (i.e. eagerness to build a nest and extent of nest elaboration). We found that male body size was associated with nesting resource size and resource architecture in the field, with the smallest males occupying small flat resources and the biggest males occupying large arched resources. In the laboratory, the type of resource occupied in the field had a limited effect on the level of nest elaboration, but not on other nesting behaviours. Large body size, in turn, was associated with preference for larger resources and, in some circumstances, also the level of nest elaboration. Body size did not affect the eagerness to initiate nest building. Furthermore, males chose arched nesting resources more often than those that were flat, and this preference was also reflected under a ‘no-choice’ scenario, based on the time taken for males to initiate nest building. Overall, the results indicate that the importance of male size in nest building is context dependent, while nesting behaviours can also be affected by resource size, resource architecture and, under some circumstances, the nest builder's experience with resource use.

Nest construction is a widespread behaviour that is a critical fitness investment in many taxa. Nests provide stable environments for offspring production, development and at times adult survival. Avian nest structure and composition has been linked to insulative properties and the reduction of energetic requirements for incubating females. However, it is unclear how and why nest structure varies across landscapes within and between species, especially in cavity-nesting species. Here we examined nest size in a secondary cavity nester, the mountain chickadee, Poecile gambeli. Nests were measured across two years at two elevations varying in ambient temperature to test whether variation in nest size was associated with local ambient temperatures and internal nest cavity microclimate. Despite both elevations having high variation in ambient temperature during nest building in both years, there were no significant relationships between multiple nest measurements and temperature. Nest size was highly consistent between years within females, suggesting that individual females are the best predictor of nest size. Large variation in nest size, internal nest cavity microclimate temperature and ambient temperature during development in one year was not associated with significant differences in reproduction; but fluctuating asymmetry, a measure of developmental stress, was significantly lower in fledglings at the higher-elevation site independent of temperature. However, there were no significant differences between elevations in the second year for any reproductive parameter. Overall, our results suggest that chickadees do not adjust nest size in response to large differences in ambient or microclimate temperature and that large variation in nest size, both across and within sites, is a result of consistent individual preferences, which do not seem to have clear fitness consequences.

Breeding success should increase with prior knowledge of the surrounding environment, which is dependent upon an animal's ability to evaluate habitat. Prospecting for nesting locations and migratory stopover sites are well-established behaviours among bird species. We assessed whether three species of California dabbling ducks – mallards, Anas platyrhynchos, gadwall, Mareca strepera, and cinnamon teal, Spatula cyanoptera – in Suisun Marsh, California, U.S.A., a brackish marsh, prospect for suitable wetlands in the week prior to brooding. K-means cluster analyses grouped 29 mallard and gadwall hens into three groups. One group (N = 13) demonstrated evidence of brood site prospecting, with the fewest and latest prebrooding wetland visits. Of these hens, seven visited their future brood pond an average of 1.14 times and only shortly before brooding (1.29 days), obtaining current information on habitat suitability. For the remaining six hens, we did not detect a brooding wetland visit, possibly due to data limitations or because these hens acquired sufficient familiarity with the wetland habitat during nest breaks in adjacent wetlands, obviating the need to prospect the specific brood pond. The second identified group of hens (N = 11) visited the brooding wetland most frequently (on 4.55 days), further in advance (5.27 days), with the fewest unique wetland visits and the earliest brooding date (26 May). The final group of hens (N = 5) were the latest to brood (21 June) and visited the most wetlands, possibly due to less water or more broods present across the landscape. Brood ponds were always farther from the nest than the nearest ponds, indicating that habitat suitability or presence of conspecifics is more important to brood site selection. Prospecting provides hens with knowledge about current habitat conditions and allows them to ‘crowdsource’ public information regarding use of that habitat by other brooding hens. Prospecting may, therefore, benefit ducks inhabiting ephemeral habitats like those within Suisun Marsh, where brood habitat is limited and water cover changes rapidly during the breeding season.

Parents increase their fitness by investing resources in offspring. However, such investment is costly for parents, leading to trade-offs, which should shift towards heavier investment in reproduction as females age and future reproductive opportunities decrease. Nests of aquatic turtles laid farther from water have higher survival than those laid closer to shore because nest predators often forage along environmental edges. However, the predation risk of adult females increases farther from water because water is used as refuge from terrestrial predators. Thus, females may balance investment in current offspring versus maternal survival and future offspring. To test whether investment varies depending upon perceived risk, we exposed 30 painted turtles, Chrysemys picta, to simulated predation by capturing and handling them shortly after females chose a nest site. We then released females, which fled to water, and allowed them to return to land and nest undisturbed. We compared the distance to water of nests laid before and after simulated predation. Unexpectedly, females did not vary distance to water in response to simulated predation. Regardless, nest sites chosen after simulated predation were more likely to be depredated than those chosen before simulated predation, suggesting that females altered nest site choice in ways we did not quantify. In addition, although older turtles nested almost twice as far from water as younger turtles, we found no evidence that age influenced maternal response to simulated predation. Our findings suggest that perceived risk of mothers to predation influences nest site choice and subsequently reduces offspring survival in C. picta. In addition, we provide a rare assessment of how plastic maternal investment might vary across reproductive life.

Many hosts of obligate brood parasitic birds invest more in parasitic nestlings than they do in their own young. The shiny cowbird, Molothrus bonariensis, a generalist parasite, is fed at a higher proportion than its host nestmates when it is reared in nests of a smaller-bodied host, the house wren, Troglodytes aedon. We test two hypotheses that could account for this differential allocation of food by host parents. The signal exaggeration hypothesis states that cowbird chicks have visual and/or acoustic begging signals that elicit preferential feeding. The size-advantage hypothesis states that hosts preferentially feed large chicks and/or that larger chicks outcompete host chicks in a scramble competition for food. To gain insight into the relative importance of size versus species-specific signals on food allocation by house wrens, we performed audio and video recordings in nests with experimental broods of (1) a 2-day-old cowbird chick and a 2-day-old wren chick (different species, different size), (2) a 2-day-old cowbird chick and an 8-day-old wren chick (different species, same size) and (3) a 2-day-old house wren and an 8-day-old house wren (same species, different size). When cowbirds shared the nest with a same-size wren chick, both chicks received food in equal proportion. In contrast, larger chicks (both cowbirds and wrens) paired with small wren nestmates always received a higher food share. Cowbird begging behaviour and call traits differed from house wrens, but these differences did not always coincide with increased food. We conclude that, at least when cowbird nestlings are young (2 days old), their relatively large size accounts for the larger share of food they receive from house wren hosts, rather than some quality of their begging signal.

Division of labour allows group-living species to efficiently complete tasks while minimizing resource expenditure. This generally involves task allocation between individuals. In territorial defence and parental care specifically, division of labour can be completed using different strategies, often involving one or more individuals defending the territory while others care for offspring. Little is known, however, about division of labour by monogamous and biparental mammals. We investigated labour division strategies across territorial defence and pup retrievals by monogamous, biparental, territorial California mice along with the role of vocal communication in coordinating these behaviours. Male and female pair-bonded California mice display aggression towards same-sex intruders and retrieve pups while alone, but how pairs complete these tasks while together remains unknown. We found that California mouse pairs used one of two strategies during territorial defence: (1) joint defence or (2) divided defence. Overall, these strategies were not altered by the intruder sex or the birth of pups. However, postpartum individuals spent more time alone in the nest and pairs spent less time together investigating intruders. Pup retrievals, conversely, followed a sex-specific strategy where mothers retrieved pups in 89% of pairs while males retrieved pups in 11% of pairs. This study shows for the first time that a monogamous and biparental rodent uses different strategies to divide labour during vital tasks of territorial defence and pup retrieval. Moreover, we found that vocal communication via sustained vocalizations were predictive of aggressive behaviour but not retrieval behaviour, indicating that vocalizations may only play a role in coordinating specific behaviours. Importantly, these strategies were task dependent and robust across intruder sex and parental status, providing a framework for better understanding division of labour in mammals.

The advantages of group living are partially offset by the cognitive challenges associated with maintaining social boundaries. These challenges can give rise to recognition mechanisms that adaptively integrate information across multiple sensory modalities. The valley carpenter bee, Xylocopa varipuncta, nests in dead wood in large aggregations of up to several dozen nests. This study investigates the proximate mechanisms by which returning foragers quickly and reliably identify their own nest entrance within a high-density nesting site. We manipulated long- and short-range visual cues associated with nest entrances, removed chemical cues on the inside of nest entrances and added chemical cues from foreign conspecific bees. By measuring the effect of these manipulations on nest search time and search accuracy, we assessed the importance of visual and olfactory sensory modalities in allowing carpenter bees to locate their nests within aggregations. Our results support the hypothesis that both visual and olfactory cues can facilitate nest localization. Removal of nest olfactory cues did not significantly disrupt homing, suggesting that olfactory information may not be necessary for nest localization when visual information is available. However, the addition of olfactory cues from unfamiliar conspecific bees actually aided nest localization rather than disrupting it, suggesting that bees may use generalized species odour cues for homing. Due to intense nest site competition within aggregations, nest localization may have important social implications for maintenance of high-density nesting.

Understanding the causes and consequences of dispersal is key to identifying selective pressures underlying species-level variation in biogeography, metapopulation dynamics and adaptive capacity. We tested the hypotheses that nest predation and/or brood parasitism avoidance drive breeding dispersal decisions and that dispersal functions to reduce subsequent reproductive failure in grasshopper sparrows, Ammodramus savannarum, breeding in eastern Kansas, U.S.A. Over 2 years, we monitored the fate of 222 nests and the movements of 144 parents. We established the spatiotemporal patterns of nest success among all nests, then related nest predation and parasitism to subsequent dispersal behaviour and reproductive success. Birds were more likely to disperse following nest predation, but decisions were unaffected by parasitism. Dispersers experienced higher chances of subsequent nest survival than did site-faithful individuals. Although second nests were parasitized less often than were first nests, dispersers did not experience substantially lower parasitism than did site-faithful individuals, suggesting that the challenges of predation and brood parasitism may be solved in different ways. This study represents one of few tests of alternative hypotheses explaining dispersal decisions of songbirds within seasons and represents a rare case study of the consequences of breeding dispersal on subsequent reproductive success. Our results suggest that differences in dispersal tendencies may result from variation in risk-response thresholds rather than alternative causal drivers.

One of the most effective defensive strategies of hosts against brood parasites is rejection, commonly achieved by ejection of the parasitic egg or desertion of the parasitized nest. Nest desertion should be a costlier strategy than egg ejection, because birds must thesn spend additional time and energy renesting, and therefore we still cannot explain why some individuals desert their nests rather than eject parasitic eggs and continue a given breeding attempt. The great reed warbler, Acrocephalus arundinaceus, is a frequent host of the common cuckoo, Cuculus canorus, and is known to use both types of rejection response. By measuring cuckoo egg mimicry, we investigated the hypothesis that the hosts desert if they cannot reliably recognize the cuckoo egg in their nest. We predicted that we would find better mimicry when hosts deserted rather than ejected. However, we did not find a difference in mimicry between these two groups of nests, implying that host females do not desert because they cannot reliably recognize the parasitic egg. We also showed that neither the date in the season nor the age of the host females influenced the type of rejection. Other factors potentially eliciting nest desertion, including host personality, host, inability to eject, excessive clutch reduction and visibility of the cuckoo female at the host nest, are discussed. Finally, we suggest that desertion may persist as a host defensive strategy against brood parasitism because it is not as costly as previously assumed and/or it is beneficial for host females in good physical condition.

Parental care is costly, and theory suggests that caregivers should reduce parental investment or even stop caring altogether when the costs of caring are too high or the benefits too low. Brood cannibalism is one tactic by which parents can divert investment away from current offspring and towards potentially higher-quality future offspring, but the various selective factors underlying partial brood cannibalism and their relative importance remain poorly understood. Here we used the plainfin midshipman fish, Porichthys notatus, to concurrently examine three hypotheses for partial brood cannibalism and test whether cannibalism increases when (1) parental body condition is low, (2) brood sizes are large and/or (3) brood paternity is low. To investigate these predictions, we combine multiyear, multisite field data with genetic paternity testing and show that partial brood cannibalism is not related to low parental body condition or to large brood sizes, but rather is linked to low paternity. In particular, males that had taken over nests from other males, and were thus unrelated to the broods present in the new nests, consumed the largest number of young (∼15 or more eaten at a time). Our data also suggest that the consumption of only a few young (∼1–2 at a time) appears to be governed by other factors that are not clearly related to paternity. Overall, we highlight the utility of concurrently testing multiple hypotheses for partial brood cannibalism within the same system to better understand this otherwise puzzling behaviour.

The maternal effect of nesting behaviour is important in oviparous species because choice of microhabitat (e.g. shade cover, temperature) can determine the environment in which embryos develop. In turn, this maternal choice can influence developmental trajectories and offspring phenotypes and survival. We studied maternal nesting behaviour in a western painted turtle, Chrysemys picta, population in northern Idaho, U.S.A. During 2013–2016, we examined maternal choice of nest microhabitat and used correlational data to quantify consequences on egg survival. In 2017, we conducted a cross-fostering experiment to decouple the effects of intrinsic maternal effects from extrinsic environmental factors on egg survival, while simultaneously manipulating the level of nest shade cover and distance from water using artificial nests. Females chose nest sites that were more open and warmer than randomly available habitat. Additionally, of three nesting areas, the coolest area with the most shade cover was used least by nesting females. Egg survival was associated with nest temperature in some, but not all, years. In the cross-fostering experiment, egg survival did not differ between natal and foster eggs, but was greater in maternal nests than in artificial nests. Additionally, egg survival increased with canopy openness and minimum nest temperature, especially for eggs in artificial nests. Overall, these results suggest that females select nesting conditions (warm and open nest sites) that positively affect hatching success.

For territorial species, the ability to be behaviourally plastic in response to changes in their social environment may be beneficial by allowing individuals to mitigate conflict with conspecifics and reduce the costs of territoriality. Here we investigated whether North American red squirrels, Tamiasciurus hudsonicus, are able to minimize costs of territory defence by adjusting behaviour in response to the familiarity of neighbouring conspecifics. Since red squirrels living in familiar neighbourhoods face reduced intrusion risk, we predicted that increasing familiarity among territorial neighbours would allow squirrels to spend less time on territorial defence and more time in the nest. Longitudinal behavioural data (1995–2004) collected from the same squirrels across several different social environments indicated that red squirrels reduced rates of territorial vocalizations and increased nest use in response to increasing familiarity with neighbours. In contrast, cross-sectional data (2015–2016), which provided observations from each individual in a single social environment, did not provide evidence of this plasticity. Post hoc analyses revealed that evidence of social plasticity in this system is primarily due to within-individual changes in behaviour, which we were unable to estimate in the cross-sectional data. Our results demonstrate that red squirrels respond to changes in their social environment by adjusting their behaviour in a manner that reduces the costs of territoriality. However, our results also suggest that estimating plasticity by comparing behaviour among individuals (i.e. cross-sectional analyses) may not always be reliable. Our ability to detect these effects may therefore depend on having data with multiple observations from the same individuals across different social environments.

The evolution of exclusive paternal care in arthropods is influenced by both natural and sexual selection. Male care may simultaneously increase egg protection against natural enemies and male attractiveness to ovipositing females. When caring males desert or die, their clutches may be adopted either by females that provide flexible compensation of parental care or by males that may increase their own attractiveness caring for unrelated eggs. Whether foster parents are as efficient as the original owner males in protecting the clutch is a question that has rarely been addressed. Here we experimentally evaluated the efficiency of egg attendance provided by males of the mud-nest harvestman Quindina limbata. We also tested whether unattended nests are adopted by females and/or unrelated males, and compared the efficiency of the protection provided by foster parents with that provided by the original owner males. We found that when males were present inside the nest, nest visits by egg predators were much lower than in experimentally unattended nests. Ten conspecifics (8 males, 2 females) adopted experimentally unattended nests. Foster males were as efficient as the original owner males in decreasing nest visits by egg predators. The most important conclusions of our study are: (1) male protection is crucial for egg survival because unattended nests are promptly attacked by predators; (2) flexible compensation of parental care by females is rare; (3) males adopt unrelated nests and protect the eggs as efficiently as original owner males, probably because egg attendance is a sexually selected behaviour.

In species with biparental care, the amount of care devoted to offspring is affected by the negotiation rules that the parents adopt. Recently, turn taking in provisioning visits has been proposed as a negotiation rule by which parents respond to their partner's behaviour, which results in a perfect alternation of the nest visits by the parents. Empirical evidence suggests that parents do not strictly alternate their visits, and, so far, this imperfect alternation has received no experimental investigation. In this study, we tested whether alternation of nest visits might be subject to time constraints affecting the ability of parents to strictly take turns. We manipulated the workload of 15 great tit, Parus major, pairs using a short-term brood size manipulation. Parental nest visits alternated more in reduced than control and enlarged broods. To understand whether this variability could be caused by changes in turn taking, we explored the rate and regularity of the parents' intervisit intervals. Treatment differences in alternation were still present when controlling for the rate and regularity of the visits by each of the two parents, suggesting that workload also affected alternation via the temporal sequence of the intervals (e.g. via turn taking). Our results show that alternation of nest visits varies in response to workload and is not merely a by-product of variation in visit rate or regularity.

The relative importance of individual and social learning in acquiring complex technological skills in animals is debated, especially the influence of processes allowing high copying fidelity (namely, imitation and teaching). We investigated how immature wild chimpanzees, Pan troglodytes troglodytes, acquired the technique for extracting underground honey. This technique is interesting because (1) adults perform exploration, pounding and perforation in nonrandom but highly flexible action sequences to locate underground bee nests, (2) they have individual preferences for how to perforate the ground and (3) the nests are deeply buried and concealed, making success difficult to achieve. We analysed the behaviour of 16 immatures recorded by camera traps at 50 sites, and tested the influence of individual attributes (namely, age and sex) and maternal behaviour; we also tested whether mothers provided learning opportunities for their offspring. We found that, as they aged, immatures of both sexes progressively matched adults' behaviour in action sequences and observed their social models more continuously. Immature males used the most common grip type used by adults for perforating (namely, the coordinated use of hands and feet) progressively more as they aged, but no effect of maternal preferences was detected. Thus, the adult technique was probably acquired via a combination of physical maturation (i.e. increased body strength and motor coordination) and observational learning, although individual learning could not be completely ruled out. Finally, the proportion of time mothers spent inactive at bee nest sites was high when they were accompanied by young daughters and decreased as daughters aged, while the opposite pattern was found for sons. Mothers may thus stimulate learning by immatures by adjusting their behaviour according to their offspring's sex and age. Overall, we showed that immature chimpanzees acquired this complex tool use behaviour via a combination of social and nonsocial learning processes, including potential maternal stimulation.

Raising a family is not free of conflict for parents, as each parent benefits when its partner provides more care for the offspring. Resolving this conflict requires cooperation between the parents. One way to achieve such cooperation might be to coordinate parental provisioning by synchronizing (i.e. returning to the nest at the same time) or alternating (i.e. taking turns) offspring provisioning at the nest. Empirical studies in birds indicate that pair coordination of the nest visits is common; however, it is unknown whether this behaviour is directly related to different outcomes of sexual conflict, such as brood desertion. We used the rock sparrow, Petronia petronia, a species with high levels of sexual conflict, to explore whether alternation and synchrony of the nest visits were related to later brood desertion. Pairs with no desertion alternated and synchronized their nest visits more than pairs in which one sex deserted. This difference in coordination was not simply a by-product of differences in provisioning by the parents. Synchrony of the visits also increased with offspring age in the pairs with no desertion. We provide evidence, for the first time to our knowledge, that the degree of parental coordination is strongly associated with the ultimate consequence of sexual conflict, brood desertion, supporting the idea that coordination in parental behaviour might promote conflict resolution.

Communication and sleep are important for humans and honey bees alike. Despite this, studies reporting consequences of sleep loss on animal communication – both signalling and receiving – are surprisingly limited. Honey bees (Apis mellifera) can famously signal the destination of a food source with a waggle dance, but when sleep-restricted, dancers perform directionally less precise dances. We analysed dance follower behaviour with respect to a dance's directional precision and whether or not the dancer had been sleep-restricted. Followers were more likely to switch dances if following an imprecise dance and more likely to exit the nest if following a precise dance. Followers were also more likely to exit the nest after following a dance composed of more iterations (waggle phases), but only if the dancer was sleep-restricted. Bees appeared to follow fewer waggle phases of a dance that was less precise, but, again, only if the dancer was sleep-restricted. Following fewer waggle phases has been shown to decrease a bee's flight accuracy, so our results suggest that cues associated with sleep loss could affect a follower's foraging success. This study presents a unique case of sender–receiver effects of sleep loss in an invertebrate, and a possible precision-dependent vulnerability in colonies of honey bees.

Constructing a nest within a mating territory provides a clear benefit to the resident, particularly by improving the opportunity to mate. It is unclear whether animals who use nests exclusively for reproductive purposes account for either the effort invested or the resulting increase in mating potential when valuing their territories. We sought to explicitly reveal a nest's added subjective resource value through within-group comparison of aggressive behaviour before and after nest construction. An increase in aggression following construction would indicate that the resident perceives greater subjective value in his territory, and thus values the nest. Threespine stickleback, Gasterosteus aculeatus, fish demonstrate stereotypical aggressive behaviours during an easily induced territorial defence. The male's nest is used exclusively for reproductive purposes, avoiding any confound of shelter. Contrary to our hypothesis, neither nest presence, timing of construction, nor nesting outcome was associated with differences in behavioural measures of territorial aggression. Assessed behaviours were robust, repeatable and inter-correlated. We conclude that territorial aggression is neither predictive of nor altered by nesting in threespine stickleback fish. Our results suggest that nests used transiently for a portion of the mating season add negligible subjective resource value to a territory. We additionally demonstrate that examinations of territorial aggression in sticklebacks do not need to control for nest building, improving statistical power by decreasing dropout rates. These results dovetail with recent work in other fish species to suggest that assessment of territorial aggression absent a nest may be practicable for fish in general.

Recently we have found that when prospecting for nests, brood-parasitic female cowbirds (Molothrus ater) vary in their use of personal and social information when selecting a nest (White, Davies, Agyapong, & Seegmiller, 2017, Proceedings of the Royal Society B: Biological Sciences, 284, 1–8), with females that are most accurate at using personal information relying least on social information and vice versa. Here, using these same female subjects, we studied whether their strategies of using social and personal information would generalize to other cognitive tasks. In two experiments we investigated whether females would attend to others when selecting a foraging site. We varied the amount of social information present and the degree of conflict that existed between personal and social information about the location of mealworms hidden in soil. We found consistency in performance within females across nest-prospecting and foraging tasks: females that were most accurate at using personal information when prospecting for nests were also most accurate at using personal information when locating food sites. Also, similar to nest prospecting, the most personally accurate females were the least dependent on social information when personal information was present. Surprisingly, however, when no personal information was present, these accurate females were most responsive to social information. Taken together, these studies suggest that females weigh the relative value of social and personal information for decisions they make and they use the most valuable information for action.

One way to characterize sociality is by the type and variability of social organization exhibited by individuals within populations. Social unit size and composition can result in costs and benefits to female group members, which may affect their reproductive success. We tested this hypothesis using data from two natural populations of prairie voles, Microtus ochrogaster , that live in habitats differing in the distribution of vegetation and in population density. During short-term investigations of populations in Indiana and Kansas (4–8 weeks), we detected significant differences between populations in the type of social units in which adult females resided, with most adult females in Kansas living as single females, whereas in Indiana most females resided in groups. However, neither social unit size nor composition was related to female reproductive success in either population. When we studied the same Indiana population for 15 weeks, the length of time that females were detected on the study grid or were residents at a nest predicted the number of offspring they produced. In addition, the number of offspring produced by females tended to decrease with group size, although this relationship was not statistically significant. Finally, social unit size was not significantly related to the amount of time females were detected in the population. Our results suggest that females do not obtain increased direct or indirect fitness by living in larger groups. Rather, persistence and residency status of females in the population are the best predictors of female reproductive success.