Patrick R. Green

Imperfect mimicry: a pigeon’s perspective

Despite the dearth of field-based evidence from natural model-mimic communities, theory suggests that Batesian mimicry should have limits placed upon the model:mimic ratio for mimics to benefit. Paradoxically, hoverflies that are apparently mimics are often superabundant, many times more abundant than their supposed models. One possible solution to this paradox is that perhaps they are not mimics at all. We use discriminative operant conditioning methods to measure the similarity perceived by pigeons between wasps and various species of supposedly mimetic hoverflies, and an image processing technique to measure objective similarity. We demonstrate that pigeons rank mimics according to their similarity to a wasp model, in an orderly broadly similar to our own intuitive rankings. Thus pigeons behave as if many hoverflies are indeed wasp mimics. However, they rank the two commonest hoverflies as very similar to wasps, despite these looking decidedly poor mimics to the human eye. In these species, ‘poor’ mimicry may have been sustainable because it exploits some constraint in birds’ visual or learning mechanisms, or some key feature used in pattern recognition. Furthermore, the relation between similarity and mimicry is nonlinear: small changes in similarity can lead to dramatic increases in the degree of mimicry.

Head Orientation and Trajectory of Locomotion during Jumping and Walking in Domestic Chicks

Patrick R. Green Department of Applied Psychology Heriot-Watt University Edinburgh EH14 4AS (UK)The relationships between the head orientation of domestic chicks and their trajectory of locomotion were examined in three tasks: jumping over gaps of different depths and widths; walking on surfaces of different slopes; and walking on a level transparent surface above a slope. Head orientation was measured as the angle between the horizontal and a line joining the centre of the eye to the beak tip. At the initiation of a jump, head angle increased with increasing depth of the gap but was not affected by gap width. During walking, head angle increased with increasing downwards slope of the walking surface and decreased with increasing upwards slope. The same effect of a downwards slope was observed when chicks walked on a level transparent surface above a slope, indicating that the effect does not depend on kinaesthetic information. The findings are discussed together with measurements of pigeon head orientation during landing flight. Explanations in terms of specialised retinal areas, binocular visual fields and lower visual field myopia are considered and rejected. It is proposed that the results instead reflect a general role of head orientation as a component in the visual control of locomotion in birds.

Optic flow-field variables trigger landing in hawk but not in pigeons

Received August 31 and November 8, 1989 1. Schmidt-Koenig, K.: Z. Tierpsychol. 18, 301 (1958); Avian Orientation and Navigation. London: Academic Press 1979 2. von Frisch, K. Experientia 5, 142 (1949); The Dance Language and Orientation of Bees. Harvard Univ. Press 1967 3. Fent, K.: J. Comp. Physiol. 158, 145 (1986) 4. Montgomery, K. C., Heinemann, E. G.: Science 116, 454 (1952) 5. Kreithen, M. L., Keeton, W. T.: J. Comp. Physiol. 89, 83 (1974) 6. Delius, J. D., Perchard, R. J., Emmerton, J.: J. Comp. Physiol. Psychol. 90, 560 (1976) 7. Delius, J. D., Emmerton J., in: Neural Mechanisms of Behaviour in the Pigeon, p. 51 (eds. Granda, A. M., Maxwell, J. H.). New York: Plenum 1979 8. Able, K. P.: J. Exp. Biol. 141, 241 (1989) 9. Moore, F. R.: Biol. Rev. 62, 65 (1987) 10. Helbig, A. J., Wiltschko, W. : Naturwissenschaften 76, 227 (1989) 11. Sandberg, R.: Condor 90, 267 (1988) 12. Hodos, W., Bessette, B. B., Macko, K. A., Weiss, S. R. B.: Vision Res. 25, 1525 (1985) 13. Umov, N.: Physik. Z. 6, 674 (1905) 14. Smith, J., in: Animal Psychophysics, p. 125 (ed. Stebbins, W. C.). New York: Appleton-Century-Crofts 1970 15. Wortel, J. F., Wubbels, R. J., Nuboer, J. F. W.: Vision Res. 24, 1107 (1984) 16. Campell, H. S., Smith, J. L.: Arch. Ophthal. 67, 501 (1962)

Multiple Sources of Depth Information: An Ecological Approach

The purpose of perceiving depth is to control behaviour within a three- dimensional world. This may involve gross locomotion of the animal within the environment, monitoring the movement of others, or movement of limbs in relation to the animal’s body and the environment. The general aims in controlling gross movement of the body are to avoid harmful collisions with objects while achieving desirable goals, as when an ostrich traverses difficult terrain while running, a guillemot alights on a cliff face without crash landing, or competing male jungle fowl time their foot strikes in order to win contests. Whether the aim is to avoid or to achieve contact with an object, successful coordination of behaviour will require relatively fast processing of information.

Head-bobbing and head orientation during landing flights of pigeons

Abstract1.The head-bobbing rhythm previously reported in pigeons Columba livia during approximately level landing flights also occurs in upwards landing flights. This finding strengthens the evidence that head-bobbing in flight is linked specifically to approach to a landing target, and that the behaviour has a visual function.2.In both level and upwards flights, head-bobbing arises from an oscillating flexion and extension of the neck. Rhythms in translation and rotation of the body do not make a detectable contribution to head-bobbing.3.Head-bobbing occurs at the same frequency as the wingbeat cycle and in a fixed phase relationship to it.4.The orientation of the head relative to the horizontal is correlated with the trajectory of upwards approach to a perch. In contrast to downwards landing flights, this relationship cannot have the function of keeping the perch in focus during landing. It is proposed instead that it enables the head to be bobbed along the axis which maximizes amplification of optic flow.

Conditioning pigeons to discriminate naturally lit insect specimens.

Pigeons (Columba livia) were trained on a visual discrimination task using a novel apparatus which enabled pinned specimens of insects, illuminated by natural daylight, to be presented under a pecking key transparent to ultraviolet light. Three birds showed evidence of learning to discriminate between sets of wasp and fly specimens. This response transferred to specimens of four hoverfly species, the strength of the response varying between the different hoverfly species. This conditioning technique offers a promising means of analysing mechanisms of visual processing in birds that are relevant to theories of the evolution of camouflage and mimicry.

Head orientation in pigeons during landing flight

Landing flights of pigeons were video recorded or filmed, and frame-by-frame measurements were made of the angle of the head relative to the horizontal, and of the position of the perch in the visual field. The angle of the head increases above that seen in free flight, to a value which is correlated with the trajectory of approach to the perch. As a result, the perch is fixated 20-25 degrees above the beak early in landing flight. The possible significance of the behaviour is discussed in relation to specialised retinal areas and to lower-field myopia.

Footedness in pigeons, or simply sleight of foot?

Gfinttirkfin et al. (1988) recently investigated footedness in pigeons by recording the foot used to remove a piece of tape from the beak. They concluded that no preference existed for the use of the right or left foot, either at the level of the population or of the individual. There are two ways in which the method used by Gfintiirkiin et al. may have obscured the existence of foot preferences. First, the assumption that placing the irritant centrally on the pigeons beak does not bias foot choice may be incorrect, as it is impossible to be certain that the tape provides symmetrical sensory input. Second, it is likely that the primary motor action involved in grooming the head is the head-neck system itself, and that any lateralization of foot use is not revealed in this context; Gtint/irkiin et al. (1988) described how the birds first attempts at removing the item involved vigorous shaking of the head. To remove any confounding effect of indirectly eliciting foot preference, we investigated asymmetry of foot use during landing and take-off flight. We filmed the landing behaviour of 16 adult homing pigeons in an outdoor flight tunnel, using a video camera providing an exposure time of 0.001 s. Six recordings of the last 30 cm of landing flight were made for each bird. A month later, those birds that had displayed marked footedness by leading consistently with either foot (on five or six landings out of six) repeated the procedure. We analysed the video recordings frame by frame to identify the leading foot. A post hoc analysis of suitable take-off flights was also undertaken, to provide a control for any effects due to physical damage to the feet. Out of 96 landing flights, the left and right foot led in 28 and 30, respectively, while neither foot was seen to lead in 38. Of 72 rake-offs, the left foot led in 12, the right foot in eight and in 52 both feet left the perch simultaneously. In neither case is there a significant population preference for one foot over the other (P> 0.05, binomial test). Individual foot preferences were scored by taking the modulus of the sum of: + 1 for trials in which the right foot led, 1 for those where the left foot led and 0 when neither foot led. For landing flight there is a bimodal distribution of foot preference; six birds used a preferred foot on five or more trials out of six (Fig. 1). This result is in sharp contrast to the unirnodal distribution of foot preference obtained by Gfintiirkfin et al. (1988), and suggests that landing behaviour reveals strong foot preferences in some birds which are not apparent in grooming behaviour. The distribution of foot preferences during take-off is unimodal, however, and reveals no birds with marked preferences (Fig. 1). This difference between foot preference in landing and take-off proved significant (Wilcoxon T = I , N = l l , P<0.01). Further, there is no evidence that foot preferences during landing flight and take-off are related, as scores in the two conditions are not significantly correlated (Pearsons r=0-16, df=9, P>005). These results confirm those of Fisher (1957), who found that 10 of a sample of 11 pigeons showed at least a 75% foot preference on landing. In addition, Fisher found that these preferences changed, in some birds, over a period of weeks. The same effect occurred when we retested the six birds with strong preferences a month later, finding that four of them had lost their preference and gave scores below five. As with Fishers data, preference fades rather than switching from one foot to another. The degree of foot preference during landing varied between pigeons, and was marked in only a minority of our sample, but variation between individuals in the strength of limb preference is the normal case in all populations. Even in the case

Problems in Animal Perception and Learning and their Implications for Models of Imprinting

A common model of imprinting holds that a representation of the imprinted object, formed in the nervous system of the young bird, is compared to later stimulus input. This “neuronal model” or “internal representation” view raises two problems, both of them general ones for understanding the organization of animal behavior. The first is the role of recognition in behavior; a number of neurophysiological, ethological and psychological theories, in giving a primary role to recognition of stimulus classes, fail to grasp the dynamic, fine-grained control of behavior by the environment characteristic of many animals, particularly the vertebrates.

Teaching Psychology in American and British Universities: Some Personal Impressions.

On the basis of our experience as British psychologists who have taught in both the United States and the United Kingdom, we make comparisons between the teaching of psychology in British and American universities. We discuss similarities and differences in course structure, curriculum, teaching methods, and evaluation procedures, and we suggest ways in which each system could benefit from some of the others practices.