Insect herbivory may cause changes in the visual properties of leaves and affect the camouflage of herbivores to avian predators

Koski, Tuuli‐Marjaana; Lindstedt, Carita; Klemola, Tero; Troscianko, Jolyon; Mäntylä, Elina; Tyystjärvi, Esa; Stevens, Martin; Helander, Marjo; Laaksonen, Toni

doi:10.1007/s00265-017-2326-0

Cited by 13 publications

(10 citation statements)

References 82 publications

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“…Estimates are means with 95% Bayesian credible intervals. For separate estimates of the visible and hidden prey designs comprising the left panel, as well as between-group differences, see Table 1 birds may still choose a foraging location based on signals from plants, because without any variation in visual information HIPVs may indicate a richer local food source or provide additional cues by, for example, affecting camouflage of prey against plant background (Koski et al, 2017) or perhaps indicating suitable foraging habitat where they are likely to find prey. Similarly in the Oriental honey buzzard, it prefers food containing olfactory pollen cues when offered visually identical options (Yang et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

Disentangling olfactory and visual information used by field foraging birds

Rubene

Leidefors

Ninkovic

et al. 2018

Ecology and Evolution

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Foraging strategies of birds can influence trophic plant–insect networks with impacts on primary plant production. Recent experiments show that some forest insectivorous birds can use herbivore‐induced plant volatiles (HIPVs) to locate herbivore‐infested trees, but it is unclear how birds combine or prioritize visual and olfactory information when making foraging decisions. Here, we investigated attraction of ground‐foraging birds to HIPVs and visible prey in short vegetation on farmland in a series of foraging choice experiments. Birds showed an initial preference for HIPVs when visual information was the same for all choice options (i.e., one experimental setup had all options with visible prey, another setup with hidden prey). However, if the alternatives within an experimental setup included visible prey (without HIPV) in competition with HIPV‐only, then birds preferred the visual option over HIPVs. Our results show that olfactory cues can play an important role in birds’ foraging choices when visual information contains little variation; however, visual cues are preferred when variation is present. This suggests certain aspects of bird foraging decisions in agricultural habitats are mediated by olfactory interaction mechanisms between birds and plants. We also found that birds from variety of dietary food guilds were attracted to HIPVs; hence, the ability of birds to use plant cues is probably more general than previously thought, and may influence the biological pest control potential of birds on farmland.

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Section: Discussionmentioning

confidence: 99%

Disentangling olfactory and visual information used by field foraging birds

Rubene

Leidefors

Ninkovic

et al. 2018

Ecology and Evolution

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“…avian insectivores (e.g. Koski et al 2017 ). Consequently, the relationship between caterpillar survival probability and leaf damage can indicate whether birds are responding to “cry for help” from trees.…”

Section: Discussionmentioning

confidence: 99%

“…Avian insectivores are likely to use both visual and olfactory cues to identify tree individuals with high abundance of insects in the foliage, but the exact mechanisms are still largely unknown (e.g. Koski et al 2015 , 2017 ).…”

Section: Discussionmentioning

confidence: 99%

Predation by avian insectivores on caterpillars is linked to leaf damage on oak (Quercus robur)

2018

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Birds that are foraging in tree canopies can cause a substantial decrease in arthropod numbers. Trees may benefit from avian insectivores attacking insect herbivores. In a field study, we tested whether the intensity of bird predation on caterpillars is linked quantitatively to leaf damage caused by insect herbivores, a hypothesized relationship that previously was poorly investigated. Artificial caterpillars were placed in the lower part of oak trees (Quercus robur) in urban and suburban sites across the city of Gothenburg, Sweden. Two days later, we recorded the survival: the pooled predation rate was 11.5% (5.7% day−1). Mean predation rate per tree was 10.4%. Mean leaf damage, i.e. leaf area eaten by insect herbivores, per tree was 5.7% but there was large variation between trees. We found a significant negative relationship between survival probability of caterpillars and leaf damage in an analysis using a mixed model logistic regression. This suggests that caterpillars are at high risk of bird attacks in trees with a high degree of leaf damage and avian insectivores may increase the foraging effort in the foliage of such oak trees. Our findings concerning the quantitative relationship between the predator–prey interactions and plant damage suggested tentatively that the survival probability of caterpillars decreases rapidly at 15–20% leaf damage in lower part of oak canopies. Furthermore, our findings add credence to the idea of using artificial caterpillars as a means to obtain standardized comparisons of predation rates in various habitats.Electronic supplementary materialThe online version of this article (10.1007/s00442-018-4234-z) contains supplementary material, which is available to authorized users.

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“…We used the Multispectral Image Calibration and Analysis Toolbox (micaToolbox) (Troscianko & Stevens, ) following the established methodology and procedure as explained in, for example, Koski et al (). With micaToolbox, we first combined human visible images and UV images to normalized and linearized multispectral images.…”

Section: Methodsmentioning

confidence: 99%

“…We used the same study specimens as in the human observer experiment and analyzed their conspicuousness to blue tits against different typical natural backgrounds with an avian vision model. To compare the contrasts of the tawny owl plumages against barks and needles of spruce and pine as well as snow, samples of these were photographed with a calibrated Fujifilm We used the Multispectral Image Calibration and Analysis Toolbox (micaToolbox) (Troscianko & Stevens, 2015) following the established methodology and procedure as explained in, for example, Koski et al (2017). With micaToolbox, we first combined human visible images and UV images to normalized and linearized multispectral images.…”

Section: Validation Of the Study Methodsmentioning

confidence: 99%

Gray plumage color is more cryptic than brown in snowy landscapes in a resident color polymorphic bird

Koskenpato

Lehikoinen

Lindstedt

et al. 2020

Ecology and Evolution

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Camouflage may promote fitness of given phenotypes in different environments. The tawny owl (Strix aluco) is a color polymorphic species with a gray and brown morph resident in the Western Palearctic. A strong selection pressure against the brown morph during snowy and cold winters has been documented earlier, but the selection mechanisms remain unresolved. Here, we hypothesize that selection favors the gray morph because it is better camouflaged against predators and mobbers in snowy conditions compared to the brown one. We conducted an online citizen science experiment where volunteers were asked to locate a gray or a brown tawny owl specimen from pictures taken in snowy and snowless landscapes. Our results show that the gray morph in snowy landscapes is the hardest to detect whereas the brown morph in snowy landscapes is the easiest to detect. With an avian vision model, we show that, similar to human perceivers, the brown morph is more conspicuous than the gray against coniferous tree trunks for a mobbing passerine. We suggest that with better camouflage, the gray morph may avoid mobbers and predators more efficiently than the brown morph and thus survive better in snowy environments. As winters are getting milder and shorter in the species range, the selection periods against brown coloration may eventually disappear or shift poleward.

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Insect herbivory may cause changes in the visual properties of leaves and affect the camouflage of herbivores to avian predators

Cited by 13 publications

References 82 publications

Disentangling olfactory and visual information used by field foraging birds

Disentangling olfactory and visual information used by field foraging birds

Predation by avian insectivores on caterpillars is linked to leaf damage on oak (Quercus robur)

Gray plumage color is more cryptic than brown in snowy landscapes in a resident color polymorphic bird

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