Monthly Archives: May 2017

Red-backed Shrikes (Lanius collurio) adjust the mobbing intensity, but not mobbing frequency, by assessing the potential threat to themselves from different predators

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2012

Martin Strnad, Michal Němec, Petr Veselý, Roman Fuchs

https://www.ornisfennica.org/pdf/latest/6Strnad.pdf

Abstract:

We studied the ability to adjust nest defence to the potential threat to defending adults and their nests in the Red-backed Shrike. We presented mounts of two raptor species which predate on adult birds (Eurasian Sparrowhawk, Common Kestrel; differing in the proportion of adult passerines in their diets), and two species of nest predators (Common Magpie, Eurasian Jay; differing in the proportion of bird eggs and nestlings in their diets). A mounted Feral Pigeon was used as a control. Shrikes regularly mobbed the Sparrowhawk, Kestrel and Jay, but not Magpie or Pigeon. The mobbing frequency, in terms of the number of mobbing events per 20 min, did not differ among the three regularly-mobbed predators. If shrikes tried to chase the predator away, they did not adjust the mobbing frequency to the level of threat to the nest. The proportion of mobbing events with physical contact (mobbing hazardousness) declined from the most mobbed Jay to the Kestrel, and to the Sparrowhawk, which was considered most dangerous. Apparently the Red-backed Shrikes adjusted the mobbing hazardousness by assessing the potential threat to themselves. Our results show the importance of a differentiation between mobbing hazardousness and mobbing frequency in the study of nest-defence behaviour.

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The responses of Central European avian predators to an allopatric aposematic true bug

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2013

Petr Veselý, Silvie Veselá, Roman Fuchs

DOI: 10.1080/03949370.2013.798351

Abstract:

A mimicry ring of red-and-black pentatomorph true bugs in Central Europe had been proposed to occur based on avoidance of its mutually non-relative members, which was confirmed based on responses of avian predators. We compared the responses of two species of European insectivorous passerines (great tit Parus major, blue tit Cyanistes caeruleus) to a typical member of the proposed ring (red firebug Pyrrhocoris apterus) and to a similarly coloured south Asian species of true bugs (red cotton bug Dysdercus cingulatus) to test if the allopatric species will be included in the proposed ring. Additionally, individuals of both bug species with colour signals artificially removed were offered to birds to assess the effect of chemical protection per se. Birds attacked the unmodified red cotton bugs more often than the red firebugs, which suggests that the birds did not include the red cotton bug in the proposed mimetic ring. Red cotton bugs were eaten by a greater number of birds than were the brown-painted red firebugs at first encounter. However, the birds quickly learned to avoid all visually unprotected bugs, suggesting that the red cotton bug possesses an effective chemical protection.

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Generalization of mimics imperfect in colour patterns: the point of view of wild avian predators

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2013

Petr Veselý, Dana Luhanová, Michaela Prášková, Roman Fuchs

DOI: 10.1111/eth.12045

Abstract:

Current research of imperfect mimicry brings ambiguous results. Experiments simulating more natural conditions rather than laboratory experiments show lower willingness of avian predators to attack less perfect mimics. We decided to simulate a natural situation by testing responses of wild-caught adult avian predators (Great tit – Parus major) to variously perfect mimics of the red firebug (Pyrrhocoris apterus), which were in previous studies shown to elicit avoidance in Great tits. Presented mimics were perfect in all traits (firebug with its own colour pattern), imperfect in colour pattern (firebug with modified colour pattern), perfect in colour pattern, but imperfect in other visual traits (cockroach with firebug colour pattern), and imperfect in colour pattern as well as in other visual traits (cockroach with modified colour patterns). Modification of the pattern focused on the rounded spots on firebug’s hemielytra, which is a conspicuous trait within the pattern. The pattern modification had no influence on the number of birds attacking the prey; nevertheless, birds spent more time observing the cockroaches that displayed the perfect firebug colour pattern than in the case of any other prey. Moreover, firebugs that displayed the perfect firebug colour pattern were observed for the shortest time (equal to that of the model – unmodified firebug). Cockroaches were attacked more often than firebugs, which suggest that birds were able to use additional visual cues (shape of legs and antennae) in prey recognition. Given these result, we conclude that differences in morphological traits characteristic for used prey taxa (true bugs, cockroaches) seem to be more important in the prey’s protection than its colour pattern.

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European checkerspots (Melitaeini: Lepidoptera, Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

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2013

Monika Tesařová, Zdeněk Fric, Petr Veselý, Martin Konvička, Roman Fuchs

DOI: 10.1111/een.12001

Abstract:

Checkerspots (Melitaeini, Nymphalidae, Lepidoptera) are usually considered a textbook example of aposematic butterflies and several studies on Nearctic species confirm this.
The responses of the avian predator, the great tit (Parus major L., Paridae, Passeriformes), to five species of Palaearctic checkerspots and one control palatable ringlet (Aphantopus hyperanthus L., Satyrinae, Nymphalidae, Lepidoptera) were observed.
None of the tested checkerspots was attacked more often than the control palatable ringlet, which suggests that birds originating from the wild had no previous bad experiences with them. Nonetheless, certain tested butterfly species (Melitea didyma, Esper; Melitea aurelia, Nickerl, and probably Melitea athalia, Rottemburg; Melitaeini, Nymphalidae, Lepidoptera) elicited some aversion in great tits (a long time handling them, a small portion of the body eaten, and some discomfort after ingestion).
Larvae of commonly eaten species (Melitea diamina, Lang; Euphydryas aurinia, Rottemburg; Melitaeini, Nymphalidae, Lepidoptera) feed on plants containing secoiridoids (in contrast to the earlier mentioned protected species, which feed mostly on plants containing iridoid glycosides); therefore the efficiency of secoiridoids in the chemical protection of butterflies is discussed.

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Nest defense of the red-backed shrike Lanius collurio against five corvid species

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2014

Michal Němec, Roman Fuchs

DOI: 10.1007/s10211-013-0175-z

Abstract:

We compared the antipredation behavior of the red-backed shrike against five European corvids including the jay, nutcracker, rook, crow, and raven. These species differ in body size and in the proportion of eggs and nestlings in their diets. The jay and nutcracker are the smallest, the rook and crow are middle-sized, and the raven being the largest corvid of all. The jay, crow, and raven are habitual nest predators, whereas the nutcracker and rook are not. The harmless pigeon was presented as a control. We analyzed (1) the number of attacks executed by shrikes against intruder presented close to shrike nests and (2) the distance between the intruder and the shrikes during the trial. The small corvids (the jay and nutcracker) were attacked significantly more intensively than the other, larger, corvids (the rook, crow, and raven) and pigeon control. All three large corvids were attacked as exceptionally as the pigeon. Shrikes approached closer to the small corvids and the pigeon than to the large corvids. These results imply that shrike antipredation strategy is adjusted to intruder size, but not to the level of intruder nest plundering specialization. Shrikes weigh up their ability to chase a given intruder away and avoid pointless aggression against large, undefeatable, intruders. This suggests that shrikes are able to asses not only the dangerousness of the intruder but also the potential advantageousness, or otherwise, of active defense.

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