I have been working on several topics related to cognitive abilities of birds in previous years. However, I do not continue work on these topics anymore.
My previous research projects resulted into three publications, which you can find here.
My previous research projects resulted into three publications, which you can find here.
Cognitive abilities of birds
The ability to avoid predators is a very important precondition for fitness in wild animals (Devereux et al. 2006). Antipredatory behavior (e.g. escape or mobbing) is usually energetically exacting (Krams & Krama 2002). In addition to direct costs, antipredatory behavior also prevents further activities, most specifically food searching. A daily repeating trade off between the need to search for food and avoid predators occurs throughout animals’ whole life (Devereux et al. 2006). Therefore, each animal confronted by a predator has to make a decision whether and what antipredatory behavior pays off. Underestimating the danger posed by an animal can be fatal. On the other hand, the evaluation of a harmless animal as threatening handicaps as well (Caro 2005).
Accurate recognition is the first step in effective predator avoidance. Predator recognition demands not only distinguishing between predators and harmless animals, but between less and more dangerous predators as well. It is well established that birds are able to discriminate between harmless and harmful animals (see Caro 2005 for review), but knowledge about the recognition and evaluation of variously dangerous predators is still poor. That is why we used feeder experiments to examine whether birds specify the antipredatory response according to predators’ dangerous.
The results support the idea that tits made a decision on the basis of threaten risk. Tits distinguished among obligatory predators (sparrowhawk, kestrel), an occasional predator (jay) and harmless birds (pigeon, thrush). Presence of both birds of prey was associated with reduced number of arrivals to a feeder to a considerable degree in comparison with the other tested birds. The presence of jay was not associated with significantly reduced number of arrivals in relation to the harmless birds, but contrary to them, with decreased number of visits in comparison to a control (feeder without dummy). Different sizes of harmless bird did not influence the tits’ behavior.
The increasing risk lowered not only the number of arrivals at the feeder but also the success of the visit and the direction of arrival to the feeder. Generally, birds assessed the risk during food searching, evaluated the situation, and adapted their behavior accordingly.
Accurate recognition is the first step in effective predator avoidance. Predator recognition demands not only distinguishing between predators and harmless animals, but between less and more dangerous predators as well. It is well established that birds are able to discriminate between harmless and harmful animals (see Caro 2005 for review), but knowledge about the recognition and evaluation of variously dangerous predators is still poor. That is why we used feeder experiments to examine whether birds specify the antipredatory response according to predators’ dangerous.
The results support the idea that tits made a decision on the basis of threaten risk. Tits distinguished among obligatory predators (sparrowhawk, kestrel), an occasional predator (jay) and harmless birds (pigeon, thrush). Presence of both birds of prey was associated with reduced number of arrivals to a feeder to a considerable degree in comparison with the other tested birds. The presence of jay was not associated with significantly reduced number of arrivals in relation to the harmless birds, but contrary to them, with decreased number of visits in comparison to a control (feeder without dummy). Different sizes of harmless bird did not influence the tits’ behavior.
The increasing risk lowered not only the number of arrivals at the feeder but also the success of the visit and the direction of arrival to the feeder. Generally, birds assessed the risk during food searching, evaluated the situation, and adapted their behavior accordingly.
Comparison of kestrel and sparrowhawk
In my second experiment, pair-wise preference experiments were used to reveal dangerous predator discrimination by four tit species, wintering in the Czech Republic. The reactions of the tits to a more dangerous predator (sparrowhawk) and a less dangerous (kestrel) one were compared. The number of visits to a feeder, with a predator present, expressed the perceived dangerousness of the predator. The tits’ behaviour towards the feeders was in agreement with predictions, according to dynamic risk assessment theory. The presence of any predator at the feeder lowered the number of visits to the feeder. Similarly, the tits were judged to have evaluated the sparrowhawk as being more dangerous than the kestrel, as its presence lowered the number of arrivals more than did the kestrel. The results not only confirm that tits behave according to dynamic risk assessment theory, but also show the exceptional suitability of preference experiments for the research of predator differentiation and evaluation.
The sign stimuli or amodal comletion? What plays the role in predator recognition?
Amodal completion enables one to perceive partly hidden objects as an entirety, and interact appropriately with them. Several studies, based upon operant conditioning, have shown that various animals (especially mammals and some birds) can perceive amodal completion. To date, the use of amodal completion by untrained animals on the recognition of objects had not yet been studied. Here, we show that tits use amodal completion in nature in their predator recognition. Using two feeders, we observed the reaction of the tits to a torso (partly occluded or an amputated dummy) of a sparrowhawk in two different treatments (torso vs. complete dummy pigeon; torso vs. complete dummy sparrowhawk). The birds clearly classified both torsos as predators, and kept away of them when the ‘pigeon’ was on the second feeder. On the other hand, when the ‘complete sparrowhawk’ was present on the second feeder, the number of visits to the occluded torso remained low; the number of visits to the amputated one increased threefold. Birds risked perching near what was clearly an amputated torso, while the fear of a “hiding” (occluded) torso remained unchanged when the second feeder did not provide a safe alternative. Such discrimination between torsos requires the ability of amodal completion. Our results demonstrate that birds in their recognition process not only use simple sign stimuli, but also complex cognitive functions. We show that the study of animal cognition can use not only operant techniques, but also field experiments with untrained animals.