Seasonal variations in bird selection pressure on prey colouration - PubMed (original) (raw)

Seasonal variations in bird selection pressure on prey colouration

Elena L Zvereva et al. Oecologia. 2021 Aug.

Abstract

The direction and strength of selection for prey colouration by predators vary in space and time and depend on the composition of the predator community. We tested the hypothesis that bird selection pressure on prey colouration changes through the season due to changes in the proportion of naïve juvenile individuals in the bird community, because naïve and educated birds differ in their responses to prey colours. Bird predation on caterpillar-shaped plasticine models in two boreal forest sites increased sevenfold from early summer to mid-summer, and the time of this increase coincides with the fledging of juvenile birds. In early summer, cryptic (black and green) models were attacked at fivefold higher rates compared with conspicuous (red and yellow) models. By contrast, starting from fledging time, cryptic and conspicuous models were attacked at similar rates, hinting at a lower selectivity by naïve juvenile birds compared with educated adult birds. Cryptic models exposed in a group together with conspicuous models were attacked by birds at a threefold lower rate than cryptic models exposed singly, thus supporting the aposematic commensalism hypothesis. However, this effect was not observed in mid- and late summer, presumably due to the lack of avoidance of conspicuous prey by the juvenile birds. We conclude that selection pressure on prey colouration weakens considerably when naïve birds dominate in the community, because the survival advantages of aposematic colouration are temporarily lost for both the conspicuous and their neighbouring cryptic prey.

Keywords: Aposematic colouration; Bird community; Cryptic colouration; Naïve predators; Plasticine models.

© 2021. The Author(s).

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Conflict of interest statement

Authors declare that there is no conflict of interest.

Figures

Fig. 1

Fig. 1

Seasonal changes in bird attack rates on plasticine models (all colours combined). Values are estimated marginal means ± SE for proportion of models attacked during one week

Fig. 2

Fig. 2

Seasonal changes in the intensities of bird attacks on plasticine models of cryptic (black and green) and aposematic (red and yellow) colours. Values are estimated marginal means + SE. Bars marked with different letters significantly differ from each other (mixed model ANOVA, t test)

Fig. 3

Fig. 3

Bird beak marks on plasticine models typical for early summer (a) and for mid- and late summer (b). Circles denote locations of weak beak marks

Fig. 4

Fig. 4

Conspicuousness of colours used in the experiment for human eye (higher rank corresponds to lower conspicuousness) (a) and bird attack rates on models of these colour in early (b), mid- (c), and late (d) summer. Values are estimated marginal means + SE for proportion of models attacked during 1 week. Bars marked with different letters significantly differ from each other (mixed model ANOVA, t test)

Fig. 5

Fig. 5

Bird attack rates on cryptic (black and green) and aposematic (red and yellow) models offered in mixed groups of all four colours and singly in a tree in different periods of season: early summer (a), mid-summer (b), and late summer (c). Values are estimated marginal means + SE for proportion of models attacked during 1 week. Bars marked with different letters significantly differ from each other (mixed model ANOVA, t test)

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References

    1. Alcock J. Punishment levels and the response of black-capped chickadees (Parus atricapillus) to three kinds of artificial seeds. Anim Behav. 1970;18:592–599. doi: 10.1016/0003-3472(70)90057-6. - DOI
    1. Alcock J. Punishment levels and response of white-throated sparrows (Zonotrichia albicollis) to three kinds of artificial models and mimics. Anim Behav. 1970;18:733–739. doi: 10.1016/0003-3472(70)90019-9. - DOI
    1. Aslam M, Nedvěd O, Sam K. Attacks by predators on artificial cryptic and aposematic insect larvae. Entomol Exp Appl. 2020;168:184–190. doi: 10.1111/eea.12877. - DOI
    1. Bohlin T, Gamberale-Stille G, Merilaita S, Exnerová A, Stys P, Tullberg BS. The detectability of the colour pattern in the aposematic firebug, Pyrrhocoris apterus: an image-based experiment with human ‘predators’. Biol J Linn Soc. 2012;105:806–816. doi: 10.1111/j.1095-8312.2011.01834.x. - DOI
    1. Chouteau M, Arias M, Joron M. Warning signals are under positive frequency-dependent selection in nature. Proc Nat Acad Sci USA. 2016;113:2164–2169. doi: 10.1073/pnas.1519216113. - DOI - PMC - PubMed

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