Through a Bird’s Eye – Exploring Avian Sensory Perception

For too many birds their environment includes airfields and aircraft. Knowing avian sensory abilities, researchers can design experiments and develop new devices and techniques to deter birds from aircraft on and away from airfields. How birds perceive the world about them determines many choices, including foraging, predator avoidance, and flight. Most experiments to investigate the sensory abilities of birds have been developed and analyzed using only human sensory capabilities, which often differ markedly from those of birds. My objective is to review and synthesize what is known and what is unknown about avian sensory capabilities. Compared with humans, birds can distinguish more colors and detect ultraviolet and polarized light directly. Their range of auditory sensitivity is narrower than humans but some species can hear sounds at least as high pitched as humans. Their chemical sensitivity is similar to humans in most cases but varies seasonally and can approach that of rodents. Avian vestibular sensitivity appears to be similar to other vertebrates but has received little investigation. There is a great deal we do not know about avian sensory perception that we need to know to make aircraft more obvious to birds and improve the effectiveness of dispersal techniques for individual species of birds. For more information on bird strikes visit http://www.birdstrikecanada. com/ and http://wildlifedamage.unl. edu Presentations of “Bird Strike 2003” Page 2 of 14 Bird Strike Committee-USA/Canada 5 Annual Meeting 18-21 August 2003, Toronto, Ontario For too many birds their environment includes airfields and aircraft. By knowing the sensory abilities of birds, researchers can design experiments and develop new devices and techniques to deter birds from aircraft on and away from airfields. How birds perceive the world about them determines many of their choices, including where to forage, what to eat, detecting and avoiding predators, and where to fly to avoid hitting objects. Most experiments to investigate the sensory abilities of birds have been developed and analyzed using only human sensory capabilities, which often differ markedly from those of birds. My objective in this paper is to review and synthesize what is known and what is unknown about avian sensory capabilities. Sensory perception can be subdivided into sensory transduction and cognition. The subject of this paper is primarily sensory transduction, converting physical phenomena to the nervous system. The nerve cells making the conversion are sensory receptors. They respond to a change in the physical signal by increasing or decreasing their rates of firing. These "firings" or nerve spikes are action potentials and the primary way that nerve cells communicate with one another. An Action Potential is an "all or nothing" response produced when the stimulus to the cell reaches the cell's threshold. In special cases, subthreshold responses can be communicated to other neurons but most communication requires the production of an Action Potential. This should be regarded as the first step in the bird's decision making process; if the receptor cell doesn't reach threshold, the information doesn't make it to the higher levels of the brain. If our objective is to cause birds to avoid aircraft, we must make sure that their receptors are stimulated enough to reach their thresholds. To make sure that objective is achieved, we have to know what those thresholds are.