Sampling methods that are both scientifically rigorous and ethical are cornerstones of any experimental biological research. Since its introduction 30 years ago, the method of using plasticine prey to quantify predation pressure has become increasingly popular in biology. However, recent studies have questioned the accuracy of the method, suggesting that misinterpretation of predator bite marks and the artificiality of the models may bias the results. Yet, bias per se might not be a methodological issue as soon as its statistical distribution in the samples is even, quantifiable, and thus correctable in quantitative analyses. In this study, we focus on avian predation of lepidopteran larvae models, which is one of the most extensively studied predator-prey interactions across diverse ecosystems worldwide. We compared bird predation on plasticine caterpillar models to that on dead caterpillars of similar size and color, using camera traps to assess actual predation events and to evaluate observer accuracy in identifying predation marks a posteriori. The question of whether plasticine models reliably measure insectivorous bird predation remained unanswered, for two reasons: (1) even the evaluation of experienced observers in the posterior assessment of predation marks on plasticine models was subjective to some extent, and (2) camera traps failed to reflect predation rates as assessed by observers, partly because they could only record evidence of bird presence rather than actual predation events. Camera traps detected more evidence of bird presence than predation clues on plasticine models, suggesting that fake prey may underestimate the foraging activity of avian insectivores. The evaluation of avian predation on real caterpillar corpses was probably also compromised by losses to other predators, likely ants. Given the uncertainties and limitations revealed by this study, and in the current absence of more effective monitoring methods, it remains simpler, more cost-effective, ethical, and reliable to keep using plasticine models to assess avian predation. However, it is important to continue developing improved monitoring technologies to better evaluate and refine these methods in order to advance research in this field.

• MeSH
• larva fyziologie   MeSH
• Lepidoptera fyziologie   MeSH
• predátorské chování * fyziologie   MeSH
• ptáci * fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Organisms have evolved different defense mechanisms, such as crypsis and mimicry, to avoid detection and recognition by predators. A prominent example is Batesian mimicry, where palatable species mimic unpalatable or toxic ones, such as Clytini (Coleoptera: Cerambycidae) that mimic wasps. However, scientific evidence for the effectiveness of Batesian mimicry in Cerambycids in natural habitats is scarce. We investigated predation of warningly and nonwarningly colored Cerambycids by birds in a temperate forest using beetle dummies. Dummies mimicking Tetropium castaneum, Leptura aethiops, Clytus arietis, and Leptura quadrifasciata were exposed on standing and laying deadwood and monitored predation events by birds over one season. The 20 surveyed plots differed in their structural complexity and canopy openness due to different postdisturbance logging strategies. A total of 88 predation events on warningly colored beetle dummies and 89 predation events on nonwarningly colored beetle dummies did not reveal the difference in predation risk by birds. However, predation risk increased with canopy openness, bird abundance, and exposure time, which peaked in July. This suggests that environmental factors have a higher importance in determining predation risk of warningly and nonwarningly colored Cerambycidae than the actual coloration of the beetles. Our study showed that canopy openness might be important in determining the predation risk of beetles by birds regardless of beetles' warning coloration. Different forest management strategies that often modify canopy openness may thus alter predator-prey interactions.

• Klíčová slova
• Batesian mimicry, beetle dummies, management intensification, natural disturbance,
• MeSH
• brouci * MeSH
• ekosystém MeSH
• lesy MeSH
• predátorské chování MeSH
• ptáci MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Several studies have shown that insectivorous birds are attracted to herbivore-damaged trees even when they cannot see or smell the actual herbivores or their feces. However, it often remained an open question whether birds are attracted by herbivore-induced changes in leaf odor or in leaf light reflectance or by both types of changes. Our study addressed this question by investigating the response of great tits (Parus major) and blue tits (Cyanistes caeruleus) to Scots pine (Pinus sylvestris) damaged by pine sawfly larvae (Diprion pini). We released the birds individually to a study booth, where they were simultaneously offered a systemically herbivore-induced and a noninfested control pine branch. In the first experiment, the birds could see the branches, but could not smell them, because each branch was kept inside a transparent, airtight cylinder. In the second experiment, the birds could smell the branches, but could not see them, because each branch was placed inside a nontransparent cylinder with a mesh lid. The results show that the birds were more attracted to the herbivore-induced branch in both experiments. Hence, either type of the tested cues, the herbivore-induced visual plant cue alone as well as the olfactory cues per se, is attractive to the birds.

• Klíčová slova
• herbivory, olfaction, systemic induction, vision, volatile organic compounds,
• Publikační typ
• časopisecké články MeSH

Insectivorous birds feed upon all developmental stages of herbivorous insects, including insect eggs if larvae and adults are unavailable. Insect egg deposition on plants can induce plant traits that are subsequently exploited by egg parasitoids searching for hosts. However, it is unknown whether avian predators can also use egg-induced plant changes for prey localization. Here, we studied whether great tits (Parus major) and blue tits (Cyanistes caeruleus) are attracted by traits of the Scots pine (Pinus sylvestris) induced by pine sawfly (Diprion pini) egg deposition. We chose this plant - insect system because sawfly egg deposition on pine needles is known to locally and systemically induce a change in pine volatile organic compounds (VOCs), and tits are known to prey upon sawfly eggs. In dual choice laboratory experiments, we simultaneously offered the birds an egg-free control branch and a systemically egg-induced branch. Significantly more birds visited the egg-induced branch first. We confirmed by GC-MS analyses that systemically egg-induced branches released more (E)-β-farnesene compared to control branches. Spectrophotometric analyses showed that control branches reflected more light than egg-induced branches throughout the avian visual range. Although a discrimination threshold model for blue tits suggests that the birds are poor at discriminating this visual difference, the role of visual stimuli in attracting the birds to egg-induced pines cannot be discounted. Our study shows, for the first time, that egg-induced odorous and/or visual plant traits can help birds to locate insect eggs without smelling or seeing those eggs.

• Klíčová slova
• Insect egg deposition, Light reflectance, Olfaction, Terpenoids, Vision, Volatile organic compounds,
• MeSH
• borovice lesní chemie   metabolismus   parazitologie   MeSH
• chování zvířat MeSH
• Hymenoptera růst a vývoj   fyziologie   MeSH
• interakce hostitele a parazita MeSH
• ovum fyziologie   MeSH
• Passeriformes fyziologie   MeSH
• plynová chromatografie s hmotnostně spektrometrickou detekcí MeSH
• seskviterpeny chemie   metabolismus   MeSH
• spektrofotometrie MeSH
• těkavé organické sloučeniny chemie   metabolismus   MeSH
• zraková percepce MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• beta-farnesene MeSH Prohlížeč
• seskviterpeny MeSH
• těkavé organické sloučeniny MeSH