Social Flocks Research Articles

Constraints on vocal production learning in budgerigars (Melopsittacus undulates)

Budgerigars (Melopsittacus undulatus) are small Australian parrots with a well-documented, learned vocal repertoire and a high degree of vocal production learning. These birds live in large, social flocks and they vocally interact with each other in a dynamic, reciprocal manner. We assume that budgerigars must process and integrate a wide variety of sensory stimuli when selecting appropriate vocal responses to conspecifics during vocal interactions, but the relative contributions of these different stimuli to that process are next to impossible to tease apart in a natural context. Here we show that budgerigars, under operant control, can learn to respond to specific stimuli with a specific vocal response. Budgerigars were trained to produce contact calls to a combination of auditory and visual cues. Birds learned to produce specific contact calls to stimuli that differed either in location (visual or auditory) or quality (visual). Interestingly, the birds could not learn to associate different vocal responses with different auditory stimuli coming from the same location. Surprisingly, this was so even when the auditory stimuli and the responses were the same (i.e., the bird’s own contact call). These results show that even in a highly controlled operant context, acoustic cues alone were not sufficient to support vocal production learning in budgerigars. From a different perspective, these results highlight the significant role that social interaction likely plays in vocal production learning so elegantly shown by Irene Pepperberg’s work in parrots.

<italic>Social Flocks</italic>: Simulating Crowds to Discover the Connection Between Spatial-Temporal Movements of People and Social Structure

Scientific studies from anthropologists, biologists, and sociologists hypothesized people who live in the geo neighborhood have more chances to contact with each other and construct the social relationships. This paper exploits a simulation-based approach to verify such hypothesis through unveiling the connection between the spatial-temporal movements of people and their social relationships. Based on the crowd simulation technique, we design an agent-based framework, social flocks, to model the geo spatial correlation of social elements. We simulate the movements of people to tackle two tasks, social network generation and network community detection. By mapping nodes in the network into agents in the simulation, we examine whether the social networks generated by our model can satisfy the network properties, such as high clustering coefficient, low average path length, and power-law degree distribution. Besides, given a social network, we simulate the social moving behaviors of agents/nodes to study the formation of communities. Experiments conducted for such two tasks verify the proposed hypotheses. Social flocks can also serve as a visualization platform for experts to explore the effects over the spatial, temporal, and social contexts. Through demonstrating how the simulation models are exploited to address social network problems, this paper encourages more studies on this direction.

Short-term immune challenge does not influence social dominance behaviour in top-ranked black-capped chickadees

In social species, groups of individuals that live, forage or interact with each other often form a linear dominance hierarchy. Dominant individuals are thought to have greater access to resources and the ability to obtain higher-quality territories or mates, making dominance rank important to maximizing fitness. Social animals are often susceptible to infections from parasites or pathogens, and the energetic cost of mounting an immune response, along with displaying sickness behaviours, could affect an individual's social relationships. If a dominant individual becomes sick and is made vulnerable to challenges from lower-ranking group members, a loss in rank could be detrimental. Many songbirds, such as the black-capped chickadee, Poecile atricapillus, form seasonal social flocks during the winter, then divide into pairs for breeding during the spring. Our study used captive chickadees to determine whether a challenge to the immune system affects social dominance behaviour and status in the winter flock. In captive experimental flocks, top-ranked individuals were given an immune challenge in the form of a lipopolysaccharide (LPS) injection, and dominance behaviour was observed to determine whether status was altered. LPS-injected individuals lost a significant amount of weight and increased feeding rate when compared to control-injected birds, indicating an energetic cost, but they showed no change in dominance behaviour or loss of rank. These findings suggest that maintaining rank by continuing to invest in dominance behaviours is important in order to retain the fitness benefits associated with a high dominance rank.

Spatial movements and social networks in juvenile male song sparrows

The time between fledging and breeding is a critical period in songbird ontogeny, but the behavior of young songbirds in the wild is relatively unstudied. The types of social relationships juveniles form with other individuals can provide insight into the process through which they learn complex behaviors crucial for survival, territory establishment, and mate attraction. We used radio telemetry to observe social associations of young male song sparrows (Melospiza melodia) from May to November. Juvenile song sparrows were frequently observed in social flocks and generally associated with more birds in the summer than in the autumn months. Most juvenile subjects formed stable social relationships with other birds and were seen with the same individual on up to 60% of the days observed. The strongest associations occurred with other juvenile males, and these individuals were often seen <1 m from the subject, even when the subject moved large distances between tracking observations. Associations also had long-term behavioral consequences as subjects were more likely to establish territories near their associates and learn shared song types. Our results indicate that male song sparrows spend a large percentage of the juvenile life stage forming social relationships and suggest that these associations may be important for the ecology of young birds and the ontogeny of their behaviors.

D1-like dopamine receptor density in nuclei involved in social behavior correlates with song in a context-dependent fashion in male European starlings

Research in songbirds shows that singing behavior is regulated by both brain areas involved in vocal behavior as well as those involved in social behavior. Interestingly, the precise role of these regions in song can vary as a function of the social, environmental and breeding context. To date, little is known about the neurotransmitters underlying such context-dependent regulation of song. Dopamine (DA) modulates highly motivated, goal-directed behaviors (including sexually motivated song) and emerging data implicate DA in the context-dependent regulation of singing behavior. This study was performed to begin to examine whether differences in DA receptors may underlie, in part, context-dependent differences in song production. We used autoradiographic procedures to label D1-like and D2-like DA receptors to examine the relationship between DA receptor density and singing behavior in multiple contexts in male European starlings ( Sturnus vulgaris). Within a breeding context (when testosterone (T) was high), D1-like receptor density in the medial preoptic nucleus (POM) and midbrain central gray (GCt) negatively correlated with song used to attract a female. Additionally in this context, D1-like receptor density in POM, GCt, medial bed nucleus of the stria terminalis (BSTm), and lateral septum (LS) negatively correlated with song likely used to defend a nest box. In contrast, in a non-breeding context (when T was low), D1-like receptor density in POM and LS positively correlated with song used to maintain social flocks. No relationships were identified between song in any context and D2-like receptor densities. Differences in the brain regions and directional relationships between D1-like receptor binding and song suggest that dopaminergic systems play a region and context-specific role in song. These data also suggest that individual variation in singing behavior may, in part, be explained by individual differences in D1-like receptor density in brain regions implicated in social behavior.

Social Foraging by Waterbirds in Shallow Coastal Lagoons in Ghana

Abstract Social foraging in waterbirds in Ghanaian coastal lagoons was studied during October and November 1994. Two types of foraging were social: directionally synchronized flocks (often involving distinctive feeding methods used in unison) and dense pecking aggregations. Social flocks were typically larger and denser than non-social flocks, and primarily involved piscivorous birds, especially the longer-legged shorebirds and egrets. It is probable that the flocks concentrate fish into temporarily high densities through herding or confusing escape reactions. We suggest that these flocks, rather than simply forming in areas of existing high prey density, may actively enhance their foraging success. There may be a true social element to either the initiation or persistence of waterbird social foraging flocks in coastal Ghana.

The effect of social dominance on fattening and food-caching behaviour in Carolina chickadees, Poecile carolinensis

Subordinates often have to wait for dominants to obtain food. As a result, their foraging success should be less predictable and they should therefore maintain a higher level of energy reserves compared with dominants. A corollary of this prediction is that subordinates should gain mass earlier in the day and maintain higher mass than dominants. We tested these predictions with captive Carolina chickadees. In two different experiments (one where birds were given ad libitum access to food and the other with food access limited to 60min/day), we formed social flocks of two previously unfamiliar birds and compared their energy management (body fat and food caches) while they were in the flock with energy management when housed alone. Results from both experiments failed to support the predictions. Of all the parameters of body mass and food caching we measured only the following results were significant: (1) On the ad libitum food schedule, both subordinates and dominants accumulated more mass over the day when in a flock compared with when they were solitary, and there were no differences in mass gain between dominants and subordinates. (2) When analysed separately, dominants showed a higher evening mass in the flock compared with the solitary condition, a trend that runs opposite to the prediction. Our results suggest that when in favourable foraging conditions, social interactions might cause dominant and subordinate birds to accumulate more energy reserves as a result of competition. On the other hand, if food supply is limited, both dominants and subordinates may be forced to maintain similar fat reserves as an insurance against increased risk of starvation.

Seasonality in basal metabolic rate and thermal conductance in a long-distance migrant shorebird, the knot (Calidris canutus)

Knots Calidris canutus live highly seasonal lives, breeding solitarily on high arctic tundra and spending the non-breeding season in large social flocks in temperate to tropical estuaries. Their reproductive activities and physiological preparations for long flights are reflected in pronounced plumage and body mass changes, even in long-term captives of the islandica subspecies (breeding in north Greenland and northeast Canada and wintering in western Europe) studied in outdoor aviaries. The three to four fattening episodes in April-July in connection with the flights to and from the high arctic breeding grounds by free-living birds, are represented by a single period of high body mass, peaking between late May and early July in a sample of ten captive islandica knots studied over four years. There are consistent and synchronized annual variations in basal metabolic rate and thermal conductance in three islandica knots. Basal metabolic rate was highest during the summer body mass peak. Within the examined individuals, basal metabolic rate scales on body mass with an exponent of about 1.4, probably reflecting a general hypertrophy of metabolically expensive muscles and organs. Any potential effect of moult on basal metabolic rate was obscured by the large seasonal mass-associated variations. In breeding plumage, insulation (the inverse of thermal conductance) was a factor of 1.35 lower than in winter plumage. This was paralleled by the dry mass of contour feathers being a factor of 1.17 lower. In this subspecies the breeding season is indeed the period during which the costs of thermoregulation are lowest. In captive knots seasonal changes in basal metabolic rate and thermal conductance likely reflect an anticipatory programme adaptive to the variable demands made by the environment at different times of the year.

Variation in numbers, territoriality and flock size of a Goldcrest Regulus regulus population in winter

A Goldcrest Regulus regulus population living in a spruce‐dominated forest near Oslo (c.60°N), in southern Norway, was studied during the winters (November‐March) from 1966–67 to 1971–72. A significant reduction in population size occurred between November and March, the recorded values varying from 76 to 96%, with a mean reduction for all six winters studied of 86%. This winter decline in numbers was significantly correlated with both precipitation (i.e., snowfall) and ambient temperature, but not with bird density. Spiders were the predominant prey items of the Goldcrests, and it is suggested that the birds experience food shortages that affect their survival rate. Although not statistically significant, a mean change in the ratio of males:females from 2:1 in October‐November to 10:1 in December—February was observed, suggesting that a greater mortality of females than males occurs during the winter.Partly based on data for colour‐banded birds, it is suggested that the Goldcrests form social flocks, which move around as individual units within territories of about 9 ha (7.5 12 ha, n= 5) in extent. The mean flock size decreased significantly from 4.57 (n= 157) birds in November‐December to 2.82 (n = 74) birds in January‐February, probably because of the reductions in the size of the local population during the winter. The mean flock size in November‐December varied inversely with the ambient temperature (r= ‐0.92).