Facultative development of courtship and communication in juvenile male cowbirds (Molothrus ater)

We investigated effects of naturally occurring variation inexperience with adult males on development of song and courtshipcompetence in captive juvenile cowbirds. We studied birds ingroups housed in large outdoor aviaries that allowed birdsto regulate access to social stimulation. In two aviaries, we housed juvenile males and females either with or withoutadult males. Birds remained in these conditions from September1999 through their breeding season. We documented social andvocal development of juvenile males in the two aviaries bymeasuring social assortment and patterns and frequencies of their song interactions. We then brought the juveniles fromthe two aviaries together to compete against each other foraccess to females. In addition, we recorded juveniles' songsfour times over the study and played back their breeding seasonsongs to females in sound-attenuating chambers to measure the effectiveness of songs in eliciting copulatory responses fromthe females. Compared to juvenile males housed with adult males,juvenile males housed without adult males developed atypicalbehavior patterns. They (1) displayed little intrasexual aggressionor near-neighbor associations and (2) exhibited different patternsof courtship and copulation, but (3) were as successful at competing for copulations. Furthermore, they developed stereotypedsongs sooner and developed more potent breeding season songs.These different outcomes could not be traced to one variablebut to a cascade of effects involving diverging patterns ofsong acquisition and social interaction. The patterns of socialskills that emerged indicate considerable plasticity in the mechanisms underlying acquisition of courtship competence.     

Pair bond characteristics and maintenance in free‐flying jackdaws Corvus monedula: effects of social context and season

Most birds rely on cooperation between pair partners for breeding. In long‐term monogamous species, pair bonds are considered the basic units of social organization, albeit these birds often form foraging, roosting or breeding groups in which they repeatedly interact with numerous conspecifics. Focusing on jackdaws Corvus monedula, we here investigated 1) the interplay between pair bond and group dynamics in several social contexts and 2) how pair partners differ in individual effort of pair bond maintenance. Based on long‐term data on free‐flying birds, we quantified social interactions between group members within three positive contexts (spatial proximity, feeding and sociopositive interactions) for different periods of the year (non‐breeding, pre‐breeding, parental care). On the group level, we found that the number of interaction partners was highest in the spatial proximity context while in the feeding and sociopositive contexts the number of interaction partners was low and moderately low, respectively. Interactions were reciprocated within almost all contexts and periods. Investigating subgrouping within the flock, results showed that interactions were preferentially directed towards the respective pair partner compared to unmated adults. When determining pair partner effort, both sexes similarly invested most into mutual proximity during late winter, thereby refreshing their bond before the onset of breeding. Paired males fed their mates over the entire year at similar rates while paired females hardly fed their mates at all but engaged in sociopositive behaviors instead. We conclude that jackdaws actively seek out positive social ties to flock members (close proximity, sociopositive behavior), at certain times of the year. Thus, the group functions as a dynamic social unit, nested within are highly cooperative pair bonds. Both sexes invested into the bond with different social behaviors and different levels of effort, yet these are likely male and female proximate mechanisms aimed at maintaining and perpetuating the pair bond.     

Does Innovation Success Influence Social Interactions? An Experimental Test in House Sparrows

In group‐living animals, individuals may benefit from the presence of an innovative group‐mate because new resources made available by innovators can be exploited, for example by scrounging or social learning. As a consequence, it may pay off to take the group‐mates' problem‐solving abilities into account in social interactions such as aggression or spatial association, for example because dominance over an innovative group‐mate can increase scrounging success, while spatial proximity may increase the chance of both direct exploitation and social learning. In this study, we tested whether the individuals' innovation success influences their social interactions with group‐mates in small captive flocks of house sparrows (Passer domesticus). First, we measured the birds' actual problem‐solving success in individual food‐extracting tasks. Then, we manipulated their apparent problem‐solving success in one task (by allowing or not allowing them to open a feeder repeatedly) while a new, unfamiliar group‐member (focal individual) had the opportunity to witness their performance. After this manipulation, we observed the frequency and intensity of aggression and the frequency of spatial associations between the focal individuals and their manipulated flock‐mates. Although flock‐mates behaved according to their treatments during manipulations, their apparent problem‐solving success did not affect significantly the focal individuals' agonistic behaviour or spatial associations. These results do not support that sparrows take flock‐mates' problem‐solving abilities into account during social interactions. However, focal individuals attacked those flock‐mates more frequently that had higher actual problem‐solving success (not witnessed directly by the focal individuals), although aggression intensity and spatial association by the focal birds were unrelated to the flock‐mates' actual success. If this association between flock‐mates' actual innovativeness and focal individuals' aggression is not due to confounding effects, it may imply that house sparrows can use more subtle cues to assess the group‐mates' problem‐solving ability than direct observation of their performance in simple foraging tasks.     

Spatial Proximity between Newborns Influences the Development of Social Relationships in Bats

Although bats are highly social mammals, the mechanisms influencing the establishment of social structures are far from being fully understood. So far, no study has addressed the effects of spatial proximity between newborns such as that occurring in nursery clusters on the development of preferential associations among individuals. We tested such effects on captive pups of Kuhl’s pipistrelle Pipistrellus kuhlii. During the first 6 wks, we kept them in separate rearing groups. Once able to fly, bats were allowed to freely interact in a common flight room, where those reared in the same groups showed higher rates of amicable interactions (proximity during roosting, allogrooming, huddling) but no effect on aggressive behaviour. Sex also influenced such frequencies, females being more likely to interact amicably. The phenomenon we describe may have significant implications for the development of bat social structures, including colony aggregation, within‐colony cryptic subunits or preferred association of individuals in fission–fusion dynamics. Our study adds a further dimension to bat sociality, highlighting the implications of spatial proximity in an early age phase.     

Do adult and juvenile dunlins Calidris alpina form randomly mixed flocks during fall migration?

Many northerly breeding shorebird species show a separation in timing of adult and juvenile migration. If, in addition to genetic control of migration, learning from experienced conspecifics is advantageous, juveniles should join adult birds during their first fall migration when possible. We here present a method to test if juveniles mix with adults during the period of overlap during southward migration, using dunlin Calidris alpina migrating over southern Sweden as an example. While taking timing differences between age classes into account, we compare flock compositions observed in the field against randomized flock‐compositions based on the pool of available individuals derived from the field data. During both the early, the adult‐dominated, and later, the juvenile‐dominated, part of the season, age classes segregate. Applied to other shorebird species, our method could be used in a comparative sense to evaluate the potential for social learning of migration routes.     

To follow or not? How animals in fusion–fission societies handle conflicting information during group decision‐making

When group members possess differing information about the environment, they may disagree on the best movement decision. Such conflicts result in group break‐ups, and are therefore a fundamental driver of fusion–fission group dynamics. Yet, a paucity of empirical work hampers our understanding of how adaptive evolution has shaped plasticity in collective behaviours that promote and maintain fusion–fission dynamics. Using movement data from GPS‐collared bison, we found that individuals constantly associated with other animals possessing different spatial knowledge, and both personal and conspecific information influenced an individual's patch choice decisions. During conflict situations, bison used group familiarity coupled with their knowledge of local foraging options and recently sampled resource quality when deciding to follow or leave a group – a tactic that led to energy‐rewarding movements. Natural selection has shaped collective behaviours for coping with social conflicts and resource heterogeneity, which maintain fusion–fission dynamics and play an essential role in animal distribution.     

Collective decision‐making and fission–fusion dynamics: a conceptual framework

Sociality exists in an extraordinary range of ecological settings. For individuals to accrue the benefits associated with social interactions, they are required to maintain a degree of spatial and temporal coordination in their activities, and make collective decisions. Such coordination and decision‐making has been the focus of much recent research. However, efforts largely have been directed toward understanding patterns of collective behaviour in relatively stable and cohesive groups. Less well understood is how fission–fusion dynamics mediate the process and outcome of collective decisions making. Here, we aim to apply established concepts and knowledge to highlight the implications of fission–fusion dynamics for collective decisions, presenting a conceptual framework based on the outcome of a small‐group discussion INCORE meeting (funded by the European Community's Sixth Framework Programme). First, we discuss how the degree of uncertainty in the environment shapes social flexibility and therefore the types of decisions individuals make in different social settings. Second, we propose that the quality of social relationships and the energetic needs of each individual influence fission decisions. Third, we explore how these factors affect the probability of individuals to fuse. Fourth, we discuss how group size and fission–fusion dynamics may affect communication processes between individuals at a local or global scale to reach a consensus or to fission. Finally, we offer a number of suggestions for future research, capturing emerging ideas and concepts on the interaction between collective decisions and fission–fusion dynamics.     

Partial migration in inexperienced pied avocets Recurvirostra avosetta: distribution pattern and correlates

Birds exhibit a range of wintering behaviour from strictly migrant to strictly resident species. In partially migrating ones, some birds overwinter within their breeding region (resident birds) while others, although breeding in the same area, winter far away (migrant birds). Accordingly, choosing a wintering region is a key stage in the annual life cycle of birds, notably for inexperienced first‐year individuals. The present study aimed to investigate this issue, and more specifically to study the distribution pattern during winter and factors influencing the wintering behaviour of first‐year pied avocets Recurvirostra avosetta. Based on a 10‐yr ringing study carried out on five of the major French breeding colonies distributed along the Atlantic coast, we showed the coexistence of different wintering tactics. The resident tactic was predominant (approximately 86% of the 575 birds re‐sighted), while the other birds adopted migration. Among resident individuals, two different tactics occurred: 43% of birds overwintered within their natal colony, whereas the others wintered in another site located at relatively close proximity along the French Atlantic coast. Hatching date was a consistent predictor of all wintering tactics. More specifically, the probability of migrating was the highest for early‐hatched birds, and for resident ones, the probability of wintering within their natal colony rather than in another French site was the highest for both median‐ and late‐hatched individuals. In addition, a colony effect was demonstrated for resident birds. Several biological interpretations, including social system, variations in both individual body condition and habitat quality, were put forward to explain these correlates.     

The Effects of Predation Risk, Food Abundance, and Population Size on Group Size of Brown-Headed Cowbirds (Molothrus ater)

Social and ecological conditions can influence flock formation (e.g. number of flocks, flock size, etc.) depending on the degree of social attraction of a species. We studied group formation in brown‐headed cowbirds (Molothrus ater) over short time periods (30 min) in two semi‐natural experiments conducted under controlled conditions. First, we determined the shape of the relationship between intake rate and flock size by manipulating group size in a single enclosure. Second, we assessed the role of population size, food abundance, and predation risk, and their interactions, in flock size formation in a system of four enclosures (two with and two without food) connected to a central refuge patch. In the first experiment, we found that pecking rates peaked at intermediate flock sizes (three to six individuals), which was influenced by greater availability of foraging time and more aggressive interactions in large groups. In the second experiment, flock sizes in the patches with food increased with population size likely due to the benefits of patch exploitation in groups. Flock size decreased after predator attack probably because refuge availability reduced perceived predation risk more than flocking in larger groups. Food abundance had minor effects, varying flock sizes between the two patches with food, under high food availability conditions when population size was high, probably due to social cohesion effects. Our results suggest that: (1) this species has an inverted‐U food intake–group size relationship with a range of intake‐maximizing flock sizes rather than a single peak, (2) the presence of a near refuge modifies the expected benefits of group patch exploitation under high predation risk, and (3) an increase in population size would more likely be translated into rapid increases in the size of the flocks rather than in more new flocks.     

Female proximity stimulates development of male competition in juvenile brown-headed cowbirds, Molothrus ater

We investigated how individual variation in social behaviour among group members interacts to affect social structure and development of reproductive skills. We randomly assigned juvenile male and juvenile and adult female cowbirds to four aviaries and observed patterns of singing and social assortment in each. Although social composition of each aviary was the same, juvenile males in one aviary engaged in more intra- and intersexual affiliation and singing interactions. We designed a series of rotations of individuals among the aviaries to determine which individual traits were responsible for the observed group differences. First, we rotated groups of three males from a less interactive aviary into a more interactive aviary, replacing interactive males. Within 4 days, the rotated males changed their behaviour to match the aviary into which they had been moved (i.e. interactive males became less interactive and vice versa). Next, we rotated juvenile females through the aviaries. After this rotation, the behaviour of the juvenile females remained the same, but the behaviour of the resident males changed, becoming like the males in the females' former aviaries (i.e. when juvenile females were moved from an interactive aviary into a noninteractive aviary, the males in the new aviary became more interactive and vice versa). Across the aviaries, the amount of female-male associations correlated positively with male-male competition. During the breeding season, males that had experienced more competition over the year received more copulations than males that had experienced little competition. Furthermore, more eggs were produced in aviaries containing competitive males than in aviaries containing less competitive males. Past work has shown that females can influence male vocal development; here we show that they can also influence male social development. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

卧龙自然保护区血雉的社群组织

１９９４年１１月至１９９５年９月在四川卧龙自然保护区五一棚地区,采用无线电追踪技术并结合野外观察,对血雉的社群组织进行了研究。血雉冬季集群活动,相邻群体相遇,有驱逐行为发生。分群配对时,雌鸟长距离迁移。血雉为单配偶制,配偶关系联结紧密,可维持整个繁殖季节。孵卵由雌鸟承担,取食时由雄鸟相伴,雌雄鸟共同育雏。繁殖季节不参加繁殖的亚成体雄鸟、参加繁殖的成体雄鸟或配偶对往往也有集群活动的倾向。在繁殖季节,     

Herd composition,kinship and fission–fusion social dynamics among wild giraffe

A variety of social systems have evolved as a consequence of competition and cooperation among individuals. Giraffe (Giraffa camelopardalis sp.) societies are an anomaly because the dearth of long‐term data has produced two polar perspectives: a loose amalgamation of non‐bonded individuals that sometimes coalesce into a herd and a structured social system with a fission–fusion process modifying herd composition within a community. We analysed 34 years of data collected from a population of Thornicroft's giraffe (G. c. thornicrofti, Lydekker 1911) residing in South Luangwa, Zambia, to establish the nature of giraffe society. Our sample consisted of 52 individually recognized animals. We found that giraffe herd composition is based upon long‐term social associations that often reflect kinship, with close relatives significantly more likely than non‐relatives to establish herds. Mother/offspring dyads had the strongest associations, which persisted for years. Giraffe live in a complex society characterized by marked flexibility in herd size, with about 25% of the variance in herd composition owing to kinship and sex. We suggest that giraffe herds share many characteristics of fission–fusion social systems and propose that sophisticated communication systems are a crucial component regulating subgroup dynamics.     

Relationship quality affects fission decisions in wild spider monkeys (Ateles geoffroyi)

Fission–fusion dynamics are thought to be mainly a response to differential availability of food resources. However, social factors may also play a role. Here, we examined whether the quality of social relationships between group members affects fission decisions. During 21 months, we collected data on social interactions and fission events of 22 spider monkeys (Ateles geoffroyi) living in a community in the protected area of Otoch Ma'ax Yetel Kooh, Yucatan, Mexico. By entering seven indexes of social interactions into a principal component analysis, we obtained three components of relationship quality, which we labelled “compatibility,” “value” and “insecurity” given the relative loadings of the indexes. Our results showed that individuals were more likely to fission into the same subgroup with community members with whom they shared higher levels of compatibility and value and lower levels of insecurity. In addition, individuals preferred to fission into the same subgroup with same‐sex group members, as expected based on what is known for the species. Our findings highlight the role of social factors in fission decisions. Adjustments in subgroup size are based on multifaceted social preferences, incorporating previously unexamined aspects of relationship quality, which are independent from overall levels of affiliative interactions.     

Spatial proximity among adult siblings in greylag geese (Anser anser): evidence for female bonding?

By staying close to allies, individuals may enjoy benefits through social support. In the socially monogamous greylag goose (Anser anser), pair-partners, parents, and even human foster parents may provide social support, facilitating access to resources or reducing agonistic pressure. In the present work, we analysed the spatial distribution of individuals within a semi-feral flock of 120 greylag geese, which contained 23 adult sibling groups of 2–4 individuals from 2 to 12 years old. During resting periods we scored dyadic distances between 28 focal individuals of different social categories, their siblings and unrelated control individuals of the same age. Adult female siblings (i.e. those hatched in the same year and raised together) rested significantly closer to each other than to either their brothers or unrelated control individuals. We attribute this to social attraction rather than to just a common preference for the same resting site. Thus, kinship bonds as expressed by cohesion might persist into adulthood, at least in the females. We discuss the potential benefits of proximity between related individuals with regard to reduced social stress via social support. Received: 21 February 2000 / Received in revised form: 16 May 2000 / Accepted: 17 May 2000     

Flock density, social foraging, and scanning: an experiment with starlings

Social foraging differs from individual foraging because italters both resource availability and the forager's behavior.We examined responses of starlings to the presence of conspecificsby manipulating foraging-group density experimentally, whileensuring that each subject's foraging opportunities were unchanged.To do this, we used individuals foraging simultaneously in fourbottomless enclosures placed at various separations in naturalforaging grounds. We measured foraging and scanning intensityand qualitative aspects of scanning of focal individuals. Additionally,we examined the temporal distribution of scanning between individuals.The focal individual analysis showed that (1) food-searchingactivity increased, while time spent scanning, time off theground and scanning bout length decreased with flock density;(2) food finding per unit of searching effort increased withdensity; (3) head orientation during scanning was sensitiveto companions' proximity: heads pointed away from the companionsat close distance, toward them at intermediate distance, andwas random farther away. The analysis of the (temporal overlappingin scanning) temporal distribution of scanning for the groupshowed that scanning was significantly synchronized when companionswere adjacent to each other but was not significantly differentfrom random at further separations. We conclude that behavioralresponses of individuals to the presence of others generateimportant changes in foraging performance even in the absenceof physical interference and, more generally, that assessingthe mechanisms that control the behavior of group members atdifferent flock densities offers a way to understand the functionaland ecological significance of foraging aggregations.     

Consistent contrast between eyelid and iris brightness supports a role for vigilance signalling in ducks

Signalling self‐ability to maintain vigilance may help in securing a mate, while providing accurate information about vigilance status may result in conspecifics adjusting their own scanning rate of the environment, potentially to the individual's benefit. In birds, vigilance is often associated with head‐up postures adopted within a bout of head‐down activity, and this can be used by conspecifics to assess the vigilance of their flock mates. However, vigilance behaviour is not always obvious and other cues may then be used to assess vigilance rates of conspecifics. Here we assess whether iris/eyelid/face patterns from 43 duck species are consistent with the hypothesis that eyelid brightness has evolved so as to contrast with iris brightness, which may then help in signalling individual vigilance status. Ducks generally flock when resting during the day, and because of their wide visual fields, individuals can monitor their environment while remaining in a resting head‐down position. Ducks also show a wide variety of plumage and iris patterns, with both light‐headed and dark‐headed species. Matching our prediction, most ducks with dark irises had pale eyelids, irrespective of head colour. Furthermore, the smaller number of species with a pale iris generally have darker eyelids. A phylogenetic analysis shows a clear and significant association in the evolution of eyelid and iris brightness patterns in both males and females. These data therefore provide support for the hypothesis that eyelid brightness has evolved to act as a contrast with iris brightness. Further studies are now needed to examine the extent to which and the way this is used in vigilance information transfer between individuals.     

Social behavior in fission–fusion groups of red uakari monkeys (Cacajao calvus ucayalii)

Primates living in large groups that divide to forage must have social systems compatible with this mode of living. Uakari monkeys (Cacajao spp.) live in large groups and exhibit a form of fission–fusion grouping, but their social organization is poorly understood. We present some of the first data on social behavior for this genus based on a study on Cacajao calvus ucayalii. They traveled in multimale multifemale groups of highly variable sizes, with bachelor units on the periphery. Adult males were affiliative, and adult females associated with more than one adult male. Adult females typically traveled with their dependent offspring and an older juvenile within the group. In parties of two or more males, individuals engaged in previously unreported display behaviors and acted together to aggressively chase other males. Breeding was seasonal, and mating occurred away from other group members. We speculate on the social organization of C. calvus ucayalii, in which dispersal may be bisexual and peripheral males are affiliative with one another. Affiliated males appear to cooperate in fighting and displaying to other males for access to females during the breeding season. Am. J. Primatol. 71:976–987, 2009. © 2009 Wiley‐Liss, Inc.     

Dusky dolphin group dynamics and association patterns in Península Valdés,Argentina

We inspected dusky dolphin (Lagenorhynchus obscurus) group dynamics in Golfo Nuevo and found differences in social organization between cold and warm seasons. Surveys were conducted onboard a research vessel, from which we collected behavioral observations and group fission‐fusion data from 2001 to 2008; we also collected photo‐identification data from 2004 to 2012. To analyze association patterns, we calculated half‐weight association index (HWI) and social differentiation (S). We conducted a Monte Carlo permutation test to determine whether observed association patterns were significantly different from random association using a compiled version of SOCPROG 2.7. Group fission and fusion dynamics depended on group behavior, the main activity after the groups' fusion was feeding, and they never fission before socializing. The social structure of dusky dolphins included long‐term preferred companions in the cold season; during the warm season, there were no preferred companions. This seasonal difference in social structure could be related to an accompanying shift in foraging behaviors that appears to be driven by changes in prey availability. If so, then a loosening of bonds among individuals during the warm season, when prey is more available, would reflect these social structure changes.     

Social carry‐over effects underpin trans‐seasonally linked structure in a wild bird population

Spatial structure underpins numerous population processes by determining the environment individuals' experience and which other individuals they encounter. Yet, how the social landscape influences individuals' spatial decisions remains largely unexplored. Wild great tits (Parus major) form freely moving winter flocks, but choose a single location to establish a breeding territory over the spring. We demonstrate that individuals' winter social associations carry‐over into their subsequent spatial decisions, as individuals breed nearer to those they were most associated with during winter. Further, they also form territory boundaries with their closest winter associates, irrespective of breeding distance. These findings were consistent across years, and among all demographic classes, suggesting that such social carry‐over effects may be general. Thus, prior social structure can shape the spatial proximity, and fine‐scale arrangement, of breeding individuals. In this way, social networks can influence a wide range of processes linked to individuals' breeding locations, including other social interactions themselves.     

Movements and Conflicts in a Flock of Foraging Black‐Tailed Godwits (Limosa limosa): The Influence of Feeding Rates on Behavioural Decisions

We studied movements and conflicts within a small flock of free‐living black‐tailed godwits foraging on benthic invertebrates in a brackish lagoon. To interpret our results in the framework of foraging theory, we studied the influence of individual feeding rate on the decisions to move and to attack flock companions. Birds changed their position within the flock more often when their intake rate was low and sometimes attacked conspecifics to supplant them from their feeding place. Aggressors significantly avoided front attacks and were almost always successful. They attacked individuals having higher feeding rates than themselves and their own feeding rate significantly increased after the attack, although victims were not chased off to particularly poor sites. Our results suggest that aggressors could obtain reliable information about the quality of the foraging site they coveted by observing their victim’s feeding activity before attacking. Although aggression seemed to be caused by a low intake rate, we show that displacing another bird was more time‐consuming than independent foraging. We conclude that it was not the most profitable behaviour in terms of energy intake. Foraging site displacement probably also had social functions, such as reinforcement of social status in a flock of birds preparing for pre‐breeding migration.