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The use of amodal completion inpredators recognition: effect on risk taking
Sedláčková, Kristýna ; Fuchs, Roman (advisor) ; Nekovářová, Tereza (referee)
Amodal completion enables animals (birds, mammals, but also fish) to perceive partly occluded objects as whole. Most of the studies focusing on the occlusion phenomenon were carried out in a laboratory and were based on either operant conditioning or filial imprinting techniques. This study concentrates on behavior of untrained animals in their natural habitat. Pairwise preferential experiments were used to reveal responses of tits (the great tit, Parus major; the blue tit, Cyanistes caeruleus; the marsh tit, Poecile palustris) to two dummies placed near an experimental and an alternative feeder. The dummies used were the complete dummy of a sparrowhawk and a pigeon, and partly occluded (the lower or upper torso hidden in shrubs) and amputated (only lower or upper torso on the perch) models of sparrowhawks - 15 combinations altogether. The tits considered all variants of torsos to be predators. The great tit and the blue tit perceived the model with occluded lower torso as more dangerous than the one with amputated lower torso. Such discrimination between these torsos requires the ability of amodal completion. The great tit also confirms this ability as it regarded the complete sparrowhawk and the model with occluded lower torso as equally dangerous. In the remaining cases, the number of arrivals...
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The effect of coloration of predator on reaction of birds at the feeder.
BURŠÍKOVÁ, Markéta
I investigate the effect of coloration of predator on the willingness of birds to undergo a predation risk at the winter feeder. I presented five colour modification of a sparowhawk and a control pigeon. The experimental species of birds presented at the feeder include great, blue, marsch and willow tits and nuthatch. My results suggest that birds are able to distinguish among the models but only in some extent. The behaviour of particular bird species differed significantly and was influenced by conditions like temperature and presence of the snow cover.
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Pigeon with sparrowhawk head: friend or enemy?
NÁCAROVÁ, Jana
The mechanism of predator recognition hasn´t been understood well yet. There are two main theoretic attitudes to this problem. Feature theory claims that animals use only some key features of the stimuli for categorization. The other opinion is that animals have a general concept how the predator should look like and local features aren't so important. We examined these theories under labor conditions. We tested the reaction of great tit (Parus major) on wooded dummies of the sparrowhawk (Accipiter nisus), pigeon (Columba livia f. domesticus) and chimeras between them that differed in the type of head. Our results show, that great tits probably use combination of both approaches to recognize the predator.
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