Dominance and anti-predator behaviour in blue tits (Parus caeruleus)

Evidence from captive flocks of blue tits (Parus caeruleus) suggests that following the appearance of a predator, socially dominant individuals are likely to wait until subordinate members of their flock resume feeding before doing so themselves. After a model sparrowhawk (Accipiter nisus) was flown over captive flocks of blue tits at a feeder, there was a significant negative correlation between sequence of return to the feeder and status within a linear dominance hierarchy. During this period, birds increased the proportion of their time budgets devoted to scanning for predators. These results suggest that during periods of danger, high-ranking individuals are able to be more cautious than are low-ranking individuals, possibly because their ability to control food resources reduces the energetic costs of their extra caution.     

Agonistic experience and individual recognition in male Quelea quelea

Male $\text{Quelea}$ were moved between groups to assess whether experience of winning or losing in new groups was correlated with their success in competition over food when they were returned to their original groups. No such effect was found. However, differences in time spent feeding after deprivation and in aggressive behaviour were found between groups depending on whether they were made up from high- or low-ranking individuals. In paired encounters there was no evidence that birds threatened unfamiliar individuals more than familiar ones or that they avoided sitting next to them more than familiar birds. This suggests that individual recognition, if it exists at all in these groups, is not important in their agonistic relationships. The rank birds occupied was correlated with beak colour, a probable measure of androgen levels, and with the amount of food consumed after deprivation. The latter result suggests that the same period of deprivation may affect some individuals more than others and this in turn may lead them to compete more for food.     

Composition of mixed‐species flocks and shifts in foraging location of flocking species on Hainan Island,China

A total of 134 bird species were recorded at Jianfengling, Hainan Island, in China from May 2000 to September 2004, of which 44 participated in one or more of 134 mixed‐species flocks. These flocks averaged 3.8 ± 0.2 species and 20.3 ± 1.2 individuals. Flocking propensity in a given species ranged from 1.5 to 100%. For flocking species, frequency of flocking and number of individuals in flocks was positively correlated with frequency and number in point counts. Among all species pairs with flocking frequency above 5%, cluster and correlation analysis indicated there were two principal groups of flocking birds – canopy species and understorey species: associations were positive within a group, but negative between groups. Canopy birds had a higher flocking propensity than understorey birds. They also made significantly less use of inner branches and trunks and greater use of middle branches, and foraged at a significantly greater height when in mixed‐species flocks than when solitary. For understorey bird species, there were no significant differences in foraging locations between solitary and mixed‐species flocks. Higher flocking frequency occurred in the wet season for canopy birds, but in the dry season for understorey birds. Overall patterns were consistent with the explanation that flocking enables an expansion of foraging niche by reducing the risk of predation.     

Clark's Nutcrackers Nucifraga columbiana Remember the Size of Their Cached Seeds

Clark's nutcrackers ( Nucifraga columbiana ) hide thousands of seeds in subterranean caches that they later recover using spatial information about cache location. In two experiments, we tested whether nutcrackers also remember another type of information regarding their caches – the size of the seeds in each cache. We videotaped birds during cache recovery and then measured their bill gape during probing behaviour as captured on the videotape. In experiment one, six birds each experienced two treatments: one that allowed them to cache and then recover large seeds, and the other, an identical treatment using small seeds. During this experiment, all six birds used a wider gape when attempting to recover seeds during the large-seed treatment than during the small-seed treatment, and gape width was significantly correlated with seed size. During experiment two, we presented birds with both large and small seeds within the same caching session. We also increased the retention interval between caching and recovery. These modifications increased the difficulty of the task. Six of the seven birds used a wider gape during seed recovery when digging for caches that contained large seeds than they did when searching for small seeds. The ability to remember the size of seeds placed within caches may serve to increase the likelihood of speedy and successful recovery. It also allows the birds another level of organization of their food supply. These are the first experiments to suggest that Clark's nutcrackers remember more about their caches than location alone.     

Bird mixed‐species flock formation is driven by low temperatures between and within seasons in a Subtropical Andean‐foothill forest

According to both the predation avoidance and foraging efficiency hypotheses, birds within mixed flocks increase their foraging efficiency and/or can spend more time feeding and less time looking out for predators. These hypotheses predict that birds in mixed flocks obtain benefits. Thus, mixed flock formation could serve as a strategy to cope with difficult conditions imposed on birds such as climatic conditions that ultimately result in a change in predation pressure or food resources. We evaluate the hypotheses that forming part of a flock confers benefits to its members and the associated prediction that birds will take advantage of these benefits and flock more often under cold and dry weather conditions between and within seasons to cope with such conditions. We surveyed the presence of mixed flocks, flocking propensity, number of species and individuals in mixed flocks in the Subtropical Yungas foothill of Argentina, to examine seasonality, flocking behavior of birds and their responses to two climatic variables: temperature and humidity. Bird species presented a higher flocking propensity and mixed flocks occurred more frequently during the dry and cold seasons than during the more benign seasons, and lower values of temperature within seasons triggered the flocking behavior. Although effects between seasons were expected, birds also showed a short‐term response to small changes in temperature within seasons. These results strengthen the ideas proposed by the foraging hypothesis. Although benefits derived from flocking have yet to be determined, whatever they are should be understood in the context of seasonal variation in life‐history traits.     

FLOCKING AND FEEDING IN THE GREAT TIT PARUS MAJOR–AN EXPERIMENTAL STUDY

Some aviary experiments designed to investigate the survival value of flocking in the Great Tit Parus major are described.
An individual searching for a source of food is less likely to find it if he is on his own or in a pair than when in a flock of four. This is a result of local enhancement: with more pairs of eyes searching, some member of the flock is likely to come across the food sooner than would a lone bird, and once one finds the food, others in the flock more or less immediately assemble at the food source. Once the birds have found a source of food, dominance interactions play a role in determining which individuals obtain the most food.
If one bird finds a single item of food, both it and the other members of the flock rapidly alter their searching behaviour, concentrating their attention in the general area and /or type of place where the food item was found.
Even if a bird searches in a place and does not find food, the others in the group show some increase in searching effort in the same area or type of place. The extent to which they do this depends on whether they are used to finding food in clumps or dispersed.
The relevance of these findings to birds in the wild is discussed. It seems likely that local enhancement does occur in natural flocks, and the flocking in Great Tits is of benefit to the participants because they increase their effectiveness in finding food. However, the question of the survival value of mixed-species flocks of titmice remains unresolved.     

Mallards Feed Longer to Maintain Intake Rate under Competition on a Natural Food Distribution

Animals foraging in groups may benefit from a faster detection of food and predators, but competition by conspecifics may reduce intake rate. Competition may also alter the foraging behaviour of individuals, which can be influenced by dominance status and the way food is distributed over the environment. Many studies measuring the effects of competition and dominance status have been conducted on a uniform or highly clumped food distribution, while in reality prey distributions are often in‐between these two extremes. The few studies that used a more natural food distribution only detected subtle effects of interference and dominance. We therefore conducted an experiment on a natural food distribution with focal mallards Anas platyrhynchos foraging alone and in a group of three, having a dominant, intermediate or subordinate dominance status. In this way, the foraging behaviour of the same individual in different treatments could be compared, and the effect of dominance was tested independently of individual identity. The experiment was balanced using a 4 × 4 Latin square design, with four focal and six non‐focal birds. Individuals in a group achieved a similar intake rate (i.e. number of consumed seeds divided by trial length) as when foraging alone, because of an increase in the proportion of time feeding (albeit not significant for subordinate birds). Patch residence time and the number of different patches visited did not differ when birds were foraging alone or in a group. Besides some agonistic interactions, no differences in foraging behaviour between dominant, intermediate and subordinate birds were measured in group trials. Possibly group‐foraging birds increased their feeding time because there was less need for vigilance or because they increased foraging intensity to compensate for competition. This study underlines that a higher competitor density does not necessarily lead to a lower intake rate, irrespective of dominance status.     

Seasonal variation in the effect of cache pilferage on cache and body mass regulation in Carolina chickadees: what are the trade-offs?

Current dynamic optimization models predict that animals shouldrespond to cache pilferage by decreasing the probability ofcaching food and by increasing internal fat storage to compensatefor a reduction in cache size. We tested these predictions underlaboratory conditions with variable food access (four 15-minintervals/day). Carolina chickadees (Poecile carolinensis) weresubjected to two environments: under pilferage conditions, one-quarterof their cached seeds were stolen every 0.5 h, and under no-pilferageconditions, seeds were left in place. Half the birds startedwith pilferage conditions and were then switched to the no-pilferagecondition; the other half started with no pilferage and werethen switched to pilferage conditions. The experiment was conductedover the course of a year to test for seasonal variation inthe response to seed pilferage. The birds responded to seedpilferage by taking more seeds from a feeder, suggesting thatthey monitored cache availability. Alternatively, the birdsmay have taken additional seeds from the feeder in responseto increased hunger caused by a loss of cached food. Contraryto our prediction, birds cached a higher percentage of seedsfrom the feeder when cached seeds were pilfered than when cacheswere left in place. Treatment order also affected caching behaviorfor all but the summer birds: chickadees initially subjectedto pilferage stored a higher proportion of seeds than thoseinitially subjected to no pilferage. Caching percentages inthe summer were unaffected by cache pilferage. Caching rates(number cached/day) also followed the same trends: rates werehigher when seeds were pilfered than when seeds were not pilfered,and there was a treatment-order effect for all but the summerbirds. Variation in body mass also failed to match predictedtrends. All birds exhibited a monotonic increase in mass asthe experiments proceeded, irrespective of treatment order.Controlling for this monotonic increase in mass, an analysisof residual variation in body mass indicated that birds gainedless weight when seeds were pilfered than when seeds were leftin place. Finally, birds tested in the fall and spring wereheavier than those tested in the summer. These results failto support the relationship between cache maintenance and bodymass regulation predicted by current models of energy regulation.We discuss the applicability of three hypotheses for the observedtrends.     

Cooperative Hunting and its Relationship to Foraging Success and Prey Size in an Avian Predator

Aplomado falcons (Falco femoralis) often hunt in pairs when chasing birds; 29% of 349 hunts observed in eastern Mexico involved mated pairs of falcons simultaneously chasing the same prey animal; and 66% of 100 hunts of birds were tandem pursuits. Although true cooperative hunting is uncommon in birds of prey, hunts by pairs of Aplomado falcons consistently showed signs of cooperative behavior such as use of a simple coordinative signal, and some division of labor between participating individuals. Pairs were more than twice as successful as solo falcons hunting birds (44% vs. 19%), however, there was no evidence that cooperative hunting increased the range of feasible prey sizes. The frequent use of cooperative foraging in this and similar species may relate to necessities of efficient nest defense, and food and nest procurement in savannas inhabited by a diversity of nest-site predators.     

Seasonal diets of red foxes in a boreal forest with a dense population of moose: the importance of winter scavenging

In Scandinavia, an increased red fox Vulpes vulpes density during the last decades has been suggested to be caused by direct and indirect human influences on food availability. Recently, attention has been focused on the role of increasing scavenging opportunities due to intensified hunting of ungulates and the reestablishment of large carnivores. In our study, we investigated seasonal and annual variations in diet composition of red fox in Varaldskogen, SE Norway, an area with cyclic voles and a high density of moose Alces alces. Analyses of scats revealed significant differences among seasons in the occurrence of ungulates—mainly moose—and ungulates were the dominating food category during winter (44.9 % of all remains). Snow tracking of red fox (71 km) in winter confirmed the importance of ungulate carcasses, i.e. one case of scavenging per 3 km. The proportions of voles were high during all seasons (11.2–28.8 %); in spite of variation in available abundances, no significant seasonal or annual differences were detected. Other food categories with seasonal variation were birds, berries/seeds and amphibians/reptiles, all more common in snow-free seasons. Our study underlines the importance of ungulate remains during periods when the abundance and diversity of alternative food sources is low. Increased and stabilized populations of red foxes—mediated through remains from hunting and wolf kills from high moose populations—might have an important effect on the population dynamics of small game. Hence, we recommend that this relationship be given attention in future studies.     

Effects of supplemental food on intra-and inter-specific behaviour of the Varied Tit Parus varius

Varied Tits Parus varius lived in flocks containing a pair, or a pair with one or two unpaired birds. To test whether the sociality of Varied Tits or their participation in mixed-species flocks is sensitive to additional food (sunflower seeds), we compared the following parameters between fed and unfed periods at the individual level: population size, degree of site fidelity, mono-specific flock size and the stability of its membership, home-range size and distribution, attendance rate with mixed-species flocks, and flock size. Neither the size of the mono-specific flock nor its membership was affected by food supply. Whether food was added or not, individuals exhibited a strong site fidelity resulting in stable population size. Supplemental feeding had no effect on home-range size or distribution. In the presence of extra food, Varied Tits were observed in mono-specific flocks but rarely in mixed-species flocks. However, when we stopped feeding, they shifted to mixed-species flocking. After adding food, mixed-species flocks were significantly smaller than in the control samples. Varied Tits were more likely to join mixed-species flocks as temperatures dropped and wind speed increased. These results suggest that intra-specific sociality of Varied Tits is relatively insensitive to food supply, but they easily shift to mixed-species flocking in relation to food and weather conditions. We conclude that Varied Tits participate in mixed-species flocks to obtain short-term benefits e.g. increased foraging efficiency but they also obtain long-term benefits from stability of pair bonds and strong site fidelity, which did not respond to supplemental food.     

Age bias in the bag of pink-footed geese <Emphasis Type="Italic">Anser brachyrhynchus</Emphasis>: influence of flocking behaviour on vulnerability

In pink-footed goose (Anser brachyrhynchus) wintering in Denmark, The Netherlands and Belgium, the proportion of juveniles in the hunting bag is consistently higher than that observed in the autumn population. Such juvenile bias in the bag is usually ascribed to young geese lacking experience with hunting or disruption of juveniles from families. An alternative explanation may be that flocking behaviour of families make juveniles more vulnerable. Observations of morning flights of pink-footed geese to the feeding grounds from two of the major autumn-staging areas showed that geese were distributed in many small flocks (median flock size = 9). This was not significantly different from the flock size distribution shot at by hunters (median = 8), suggesting that hunters targeted goose flock size in proportion to the general probability of encounter. The rate at which hunters downed geese was independent of flock size. The ratio between juveniles and adults in flocks decreased with flock size and flocks of <60 individuals primarily comprised family groups. The likelihood of being shot at was 2.4 times higher for juveniles and 3.4 times higher for older birds in small flocks (<10 individuals) compared to larger flocks. The observations suggest that both juveniles as well as successful adult breeding birds were more vulnerable than non-breeding/failed breeding birds as a result of flocking behaviour.     

Social learning influences the preferences of domestic hens for novel food

It has been argued that social learning helps animals either avoid noxious substances or identify food items, but evidence suggests that avian social learning is fundamentally different from that of mammals. In two experiments, we investigated whether the preferences of domestic hens, Gallus g. domesticus, for novel food were influenced by observing the feeding behaviour of conspecifics. In experiment 1, we attempted to confirm that birds can develop socially learnt aversions to unpalatable foods. Despite demonstrators showing a highly visible ‘disgust reaction’ after eating unpalatable coloured food, observers did not develop aversions to similarly coloured food. In experiment 2, we aimed to determine whether preferences for palatable food were socially learnt, and whether the extent of a demonstrator's preference for novel food affected the magnitude of the observer's socially learned preference. Demonstrators ate coloured food of standard or high palatability, or did not peck food at all. When the demonstrators pecked more frequently or fed more quickly from the food, the observers consumed a greater proportion of food of the same colour; however, this was only when the food was red, not green. We argue this indicates an unlearned aversion to red food, overcome by social learning of the food being highly palatable. The results provide no evidence that adult hens learn aversions through observing disgust reactions, but show that hens are sensitive to the extent of demonstrator preferences for palatable food. The data do not support the hypothesis that avian social learning is fundamentally different from that of mammals. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Foraging strategy and predator avoidance behaviour: an intraspecific approach

Relationships between predator avoidance behaviour (scanning and flocking) and foraging were studied in Calidris alpina, to test predictions regarding the effect of foraging techniques on such behaviours. The scanning hypothesis predicts that individuals with a tactile hunting technique and individuals with a visual hunting technique (both continuous searchers) do not differ in any variable related to scanning behaviour. The flocking hypothesis predicts that visually hunting individuals witl tend to form smaller flocks than tactile-foraging individuals. The two continuous feeding strategies did not differ among individuals in vigilance rate, nor in vigilance time or mean scan duration. However, with respect to flocking behaviour, visual foragers differed from tactile foragers in foraging flock size. The relationships between flocking behaviour and foraging strategy are discussed. The pattern found at the intraspecific level are the same as those found at interspecific level.     

金秀大瑶山瑶民“鸟盆”狩猎区鸟类食物源植物及生态保育

2003年7月～2008年12月,对金秀大瑶山茶山瑶民"鸟盆"狩猎活动区域的鸟类食物源植物进行了调查,录得"鸟盆"狩猎区秋冬季鸟类取食果实、种子的植物有28科71种,当地称为"鸟果"树。此外,瑶民"鸟盆"狩猎活动所需的"鸟漆"(粘捕鸟类的粘胶)是用9种冬青科植物的树皮制作,其果实、种子亦是"鸟盆"狩猎活动区鸟类的主要食物。     

Predation by Australian magpies (Gymnorhina tibicen) on pasture invertebrates: Are non-territorial birds less successful?

Diet composition and prey intake rates of Australian magpies in a New Zealand population were investigated to determine whether flocking, non-territorial birds were less successful predators of pasture invertebrates than territorial birds. Time-activity budgets showed that flock magpies foraged throughout the day during February and March, indicative of a prey shortage at that time. Prey abundance was therefore measured in the autumn months but there was no evidence of a large quantitative difference in the food supply of flock and territorial magpies. Significantly fewer invertebrates were collected from pitfall traps in the flock foraging area, but these were counterbalanced by significantly more scarab beetle larvae and more flying insects, obtained by sweep-netting. When compared with territorial magpies, flock birds exhibited similar peck rates, prey intake rates, and earthworm intake rates. While there were qualitative differences in the diets of flock and territorial magpies, determined by faecal analysis, five of seven prey items analysed were captured in the same relative proportions by the flock and territorial birds. Earthworms exceeded their relative availability in the diets of flock birds, and more scarab larvae were found in the diets of territorial magpies. Non-territorial magpies were therefore no less successful than territorial birds during the autumn, and it is suggested that the function of flocking behaviour may eventually be discovered through consideration of why non-territorial birds never occur as solitary individuals, rather than emphasizing comparisons with territorial magpies.     

Effects of hunting on guianan forest game birds

To assess the effect of on-going and of previous or near by hunting pressure on game birds in a neotropical rain forest (French Guiana), I compared species abundances between six hunted and disturbed areas, seven non-hunted and pristine areas and eight intermediate areas, undisturbed and not currently hunted, but formerly hunted or close to current hunting areas. I recorded all birds detected within 100 m-wide strip transects, walked at random through every forest type all day long. The frequency of records per 10 h and flock sizes on each transect were averaged over all surveys in each study site (N = 3025 h). Censused groups included terrestrial (tinamous, woodquails, curassow and trumpeter) and arboreal species (guans, macaws, parrots, toucans), but not waterbirds. The abundance of all game birds was higher in non-hunted than in hunted areas, though not always significantly for secretive understorey species (tinamous, guans, wood-quail) or canopy frugivores (parrots, macaws, toucans). The Black Curassow and Gray-winged Trumpeter exhibited the highest and most consistent increases (7–10-fold) and more so between intermediate and non-hunted sites than between hunted and intermediate sites. The mean flock size also increased along the hunting gradient, especially in flocking species (macaws, parrots, trumpeter). Low reproductive rates and/or seasonal movements may explain that hunting pressure could still be felt after hunting has ceased or when it persists only away from a given area. Such a persistent effect would affect some populations in small protected areas.     

同种竞争压力对小泡巨鼠贮藏油茶种子行为的作用分析

2002年11～12月,在四川省都江堰地区的亚热带常绿阔叶林内利用人工修建的半自然状态围栏进行实验,研究了小泡巨鼠在有同种竞争存在条件下对油茶种子的埋藏行为。结果表明,小泡巨鼠在有竞争存在条件下,显增加了埋藏油茶种子的量。这一结果支持了“竞争的存在刺激鼠类埋藏”的假说。同时,研究结果表明,小泡巨鼠在有竞争存在条件下,显增加了对埋藏种子的搬运距离,每个贮藏点埋藏种子的数量也有所增加,同时埋藏的生境更多地偏向于遮蔽较好的微生境(草丛底层、灌丛下层)中。这些行为策略有可能有利于种子被埋藏植物的种群扩散。在讨论中,我们还通过比较鸟类和兽类在感觉器官上的差别,分析它们在有竞争存在条件下所采取的不同贮食策略。     

Bowing and allopreening of captive Jackdaws Corvus monedula

Allopreening interactions were observed in groups of captive, hand-reared Jackdaws Corvus monedula. Head fluff and Bowing, both resembling 'soliciting' postures described in the literature, are described. Head fluff seems to be associated with allopreening. Bowing was performed more frequently by socially top-ranking birds, performed and received equally frequently by females and by males, and directed at birds higher than and lower than the performer with equal frequency. Bowing was followed mostly by the recipient's moving away or by no apparent response, and only rarely by the allopreening of the actor. Allopreening was performed mostly by socially low-ranking towards high-ranking birds, and both when the actor was dominant to or submissive to the recipient. Bowing and allopreening seemed to be associated with situations of tension. It is suggested that Bowing here was used as intimidation rather than 'solicitation' or appeasement, and that allopreening and Bowing function in confirming relationships and in conveying information about relative status to other members of the group.     

Memory for the location of stored food in marsh tits

Marsh tits store several hundred food items per day, in separate locations within their territory, and recover most items within 24 h. Experiments in the laboratory determined that marsh tits return accurately to the sites of stored sunflower seeds 3 h and 24 h after storage. The proportion of returns exceeded chance encounter and initial preferences for those sites. The lack of interocular transfer in birds for some visual tasks provided a test for the hypothesis that memory is used to relocate stored food. After storing food with one eye covered, marsh tits did not return to storage sites when using only the ‘naive’ eye, but did so when using only the eye uncovered during storage. It seems likely that recovery of stored food by marsh tits and other birds occurs by memory of storage sites, not by chance encounter during foraging.