Aggregate Dispersion of Birds after Encountering a Predator: Experimental Evidence

Forsman, Jukka T.; Mönkkönen, Mikko; Inkeröinen, Jouko; Reunanen, Pasi

doi:10.2307/3677339

Cited by 47 publications

(28 citation statements)

References 22 publications

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“…This is consistent with the general presence of super-aggregation in adversity [1][2][3][4][5]7], but of course does not rule out additional mechanisms in particular situations, such as collective protection or confusion effects in the case of predation risk. Interestingly, our approach also makes predictions that are probably different from other explanations.…”

Section: Discussionsupporting

confidence: 64%

“…This phenomenon is well documented in groups of moving animals, which often form tighter groups in response to the detection of a predator [1][2][3][4][5][6]; but it also takes place in other adverse conditions, such as in the absence of food [7] or when animals are introduced into an unknown environment [8,9]. In humans, the occurrence of sudden bank runs [10][11][12] and human stampedes [13 -19] suggests increased aggregation in adversity, although data are insufficient to draw definitive conclusions.…”

Section: Introductionmentioning

confidence: 99%

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Adversity magnifies the importance of social information in decision-making

Pérez‐Escudero

Polavieja

2016

Preprint

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Decision-making theories explain animal behaviour, including human behaviour, as a response to estimations about the environment. In the case of collective behaviour, they have given quantitative predictions of how animals follow the majority option. However, they have so far failed to explain that in some species and contexts social cohesion increases when conditions become more adverse (i.e. individuals choose the majority option with higher probability when the estimated quality of all available options decreases). We have found that this failure is due to modelling simplifications that aided analysis, like low levels of stochasticity or the assumption that only one choice is the correct one. We provide a more general but simple geometric framework to describe optimal or suboptimal decisions in collectives that gives insight into three different mechanisms behind this effect. The three mechanisms have in common that the private information acts as a gain factor to social information: a decrease in the privately estimated quality of all available options increases the impact of social information, even when social information itself remains unchanged. This increase in the importance of social information makes it more likely that agents will follow the majority option. We show that these results quantitatively explain collective behaviour in fish and experiments of social influence in humans.

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Section: Discussionsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Adversity magnifies the importance of social information in decision-making

Pérez‐Escudero

Polavieja

2016

Preprint

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“…Nevertheless, it is an interesting effect taking into account that the prey species studied are not considered to form inter-specific aggregations during the breeding season. Similar seasonal responses were found in forest passerines, which clumped their breeding territories when the perceived risk of predation increased (Forsman et al 1998). The tendency to form aggregations in our system may be accounted for by the lower probabilities of magpies attacking groups, and the lower chances of prey being caught if an attack occurred due to dilution effects (e.g., Whitfield 2003).…”

Section: Predation Patternssupporting

confidence: 59%

Effects of opportunistic predation on anti-predator behavioural responses in a guild of ground foragers

et al. 2004

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We studied factors that affect prey selection by a generalist predator that opportunistically attacks prey species, and the associated inter- and intra-specific responses of prey to this type of predation. Our model system was a guild of ground-foraging birds that are preyed upon by magpies ( Pica pica) during the breeding season. We found that magpies attacked up to 12 species during three consecutive breeding seasons. The overall capture success was estimated to be 4.9%. Magpies tended to attack from the air, targeting solitary prey, either on the ground or flying. Inter-specific prey responses to the risk of magpie predation included a reduction in the mean number of species occupying a foraging patch when magpies were present and a decrease in the distance between heterospecific neighbours. Intra-specific responses to magpie predation varied between species that were subject to different attack rates. Preferentially attacked prey enhanced their risk responses (increase in scanning time and scanning rate in the presence of magpies) relative to those species attacked in proportion to their abundance (increase only in scanning rate with magpies). Species attacked infrequently, relative to their abundance, showed no antipredator response. The probability of being attacked, rather than mortality rate, appears to be the factor to which prey species respond.

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“…A stronger reaction to a more dangerous predator was observed in most of the studies (falcons vs. hawks vs. eagles vs. great horned owl Buteo virginianus, Buitron 1983; sparrowhawk vs. pygmy owl Glaucidium passerinum vs. tawny owl Strix aluco, Curio et al 1983; sparrowhawk vs. pygmy owl, Rytkönen and Soppela 1995;Forsman et al 1998). Griesser (2009) compared jay reactions to three hawk and three owl species (goshawk Accipiter gentilis, sparrowhawk Accipiter nisus, hobby Falco subbuteus, Ural owl Strix uralensi, hawk owl Surnia ulula, pygmy owl Glaucidium passerinum) of varying danger, and the jay's ability to communicate the threats.…”

Section: Discussionmentioning

confidence: 93%

Tits recognize the potential dangers of predators and harmless birds in feeder experiments

Tvardíková

Fuchs

2011

J Ethol

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Accurate recognition of a predator is the necessary precondition for adequate antipredatory behaviour. We used feeder experiments to examine whether birds adopt the appropriate antipredatory response according to the level of threat posed by predators. The results support the idea that the tits made a decision on the threat level. The tits distinguished among equally sized obligatory predators (sparrowhawk, kestrel), an occasional predator (jay) and a harmless bird of similar size (pigeon) and a smaller harmless bird (thrush). The presence of both birds of prey was associated with a considerable reduction in the number of feeder visits when compared with the harmless birds. The number of visits to the feeder that had a dummy jay positioned on it did not significantly differ for harmless birds or for predators. Different sizes of harmless birds did not influence the tits' behaviour. The increasing risk lowered not only the number of visits to the feeder but also the success of the visit, pecking rate, and the direction of arrival to the feeder. Generally, birds assessed the risk during food searching, evaluated the situation, and adapted their behaviour accordingly.

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Aggregate Dispersion of Birds after Encountering a Predator: Experimental Evidence

Cited by 47 publications

References 22 publications

Adversity magnifies the importance of social information in decision-making

Adversity magnifies the importance of social information in decision-making

Effects of opportunistic predation on anti-predator behavioural responses in a guild of ground foragers

Tits recognize the potential dangers of predators and harmless birds in feeder experiments

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