Crypsis and search image

Birds as predators

Most animals avoid predation by possessing a cryptic colouration i.e. a colouration matching most of the natural backgrounds. This strategy increases demands on the predators’ ability of searching for food. Most visually orienting predators therefore developed a special foraging technique, called search image. A predator searching for a familiar prey is able to find it quicker than an unfamiliar item. One can also argue that a predator would create an internal representation of a previously rewarded object, i. e. palatable food, for which it would be then seeking. This “expectation” can thus affect visual search of prior information about possible targets. Visually oriented predators might be able to exploit the cryptic food source more efficiently when by learning its features they can distinguish it easier from the background. This strategy therefore fulfils the demands and expectation of the theory of Optimal foraging. Nevertheless, this ability is substantially affected by the level of dietary wariness of particular predators. All species differ in the width of acceptable food and thereby in the level of their specialization. Different species show different levels of neophobia, when encountering a novel food, different times after which the neophobia vanishes and different ability/willingness to learn to utilize a novel food source. This variability substantially limits the ability to develop a search image, i.e. to include some food item among the preferred and desired ones. Our research focuses on the ability of various bird species to find a cryptic food item, both when novel or familiar. Further we investigate how efficiently the birds are able to collect these food items and how easily their skip to another food source (again familiar and /or novel).

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