Olfactory intensity-difference thresholds in the pigeon

Behavioral correlates of olfactory and trigeminal gaseous stimulation in chickens, Gallus domesticus

Despite growing evidence of avian olfactory abilities, there are few reports of behavioral correlates of chemosensory stimulation in birds. The present study aimed to determine how the behavioral responses of hens to selected gases might be affected by input from different chemosensory systems. We also hoped to relate electrophysiological thresholds previously measured in our laboratory to behavioral evidence of perception. Immediate behavioral responses to ascending series of short (7 s) pulses of olfactory (hydrogen sulphide), trigeminal (carbon dioxide) and combining (ammonia) gaseous stimulants were measured in 12 partially restrained adult hens (Gallus domesticus) using a purpose built gas delivery system. The concentration ranges applied matched those used in our previous electrophysiological studies of olfactory bulb responses. Consistent and specific behavioral responses were observed in response to stimulation with each gas. While significant increases in mandibulation (a distinctive rapid bout of bill movements), interruption of ongoing behavior, orientation to the end of the stimulus, and struggling were seen during stimulation with all three gases, orientation towards the stimulus occurred only in response to the olfactory stimulants, ammonia and hydrogen sulphide. The only gas to elicit significant avoidance was hydrogen sulphide, while gasping and headshaking were elevated in response to stimulation with carbon dioxide. Approximate threshold values for some types of behavior related reasonably well to receptor thresholds determined electrophysiologically, but perception may have occurred at lower concentrations without overt behavioral consequences. The diversity of the behavioral responses observed supports the notion that the gases selectively stimulated different sensory pathways.

Neuroethological aspects of avian orientation

Sensory information, which may be essential for the complex process of orientation of birds, is described in this article. The use of vibrational, visual, chemical, olfactory, magnetic cues and their receptive mechanisms, as far as they are known, are explained. Special reference is given to the behavioral and physiological aspects of magnetic sensitivity.

Sensory basis of bird orientation

Sensory information which may be essential for the complex process of orientation of birds is described in this article. The use of vibrational, visual, chemical, olfactory, magnetic cues and their receptive mechanisms, as far as they are known, are explained. Special reference is given to the behavioral and physiological aspects of magnetic sensitivity.

Interhemispheric transfer of olfactory information in homing pigeon

The role of the anterior commissure in discrimination of and habituation to olfactory stimuli was studied in pigeons by measuring changes in the heart rate. In order to exclude any trigeminal response, we presented odorous stimuli to groups of pigeons with one olfactory nerve cut and either the ipsilateral or the contralateral nostril plugged. When the nostril involved in the experiments was on the same side of the cut olfactory nerve, the pigeons did not show any response, whereas they displayed changes in heart rate when the nostril tested was on the opposite side. In habituation transfer experiments were a control group of pigeons and a group with the anterior commissure cut, both of them subjected to a monolateral habituation training to amylacetate. Later, when the odour was presented to the opposite nostril, both groups maintained the habituation.

Odor psychophysics in vertebrates

The methods used to obtain psychophysical data on the nasal chemosensory systems of all classes of vertebrates are critically reviewed and a summary of the available data on their odor detection and discrimination abilities is provided. Although there are reliable methods for training at least one member of each class to respond differentially to the presence or absence of odor stimuli, very little is known about the limits of the capacity of any of the three major nasal chemosensory systems (olfactory, vomeronasal and trigeminal) to detect pure compounds. Furthermore, studies in which rigorous procedures are followed for both the maintenance of discriminative responding and the presentation of odor stimuli often fail to determine the sensory system(s) mediating the psychophysical results. This lack of information has impeded progress on several fundamental problems in the study of nasal chemoreception.

An operant procedure for testing olfactory capacities in restrained pigeons

A psychophysical procedure was developed to test the olfactory capacities of the pigeon. The procedure employs symmetrical response contingencies, involves the confinement of the pigeon's head in the stimulus air stream and relies solely on positive reinforcement for the development and maintenance of discriminative responding. The absolute sensitivity of three pigeons to amyl acetate in air was measured. Thresholds for all three pigeons were between 10(-3.4) and 10(-3.6) of vapor saturation.

Social olfaction: a review of the role of olfaction in a variety of animal behaviors

Behavioral olfactory experiments were reviewed, relating the behavioral effects of pheromones to the psychophysical work in olfaction. Short descriptions of various experiments were used to show the importance of olfaction to the social behavior of animals by tracing the history of the experimental evidence and viewing the behavioral data pertaining to the discharge of pheromones and their effects and to look at the psychophysical evidence for olfactory acuity and the behavioral implications for the role of the physiological structures in olfaction.