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Author Kacelnik, A.
Title The foraging efficiency of great tits (Parus major L.) in relation to light intensity Type Journal Article
Year 1979 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 27 Issue Part 1 Pages 237-241
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Abstract I report an experiment aimed at testing whether foraging efficiency of great tits is limited by light intensity at the time of the dawn chorus. Captive great tits hunting for prey under different luminance conditions were less successful in finding prey when foraging, hunted for a lower proportion of their time, and handled individual prey items for longer when luminance was under approximately 7 cd/m2. This luminance is not reached in the field until after the time of the dawn chorus, suggesting that in the early morning foraging is limited by light intensity. I suggest that a satisfactory functional explanation of the dawn chorus must take into account the comparatively low foraging opportunity early in the morning, as well as the factors affecting the opportunity for singing and other territorial activities.
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Call Number Serial 2125
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Author Kacelnik, A.
Title Information primacy or preference for familiar foraging techniques? A critique of Inglis & Ferguson Type Journal Article
Year 1987 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 35 Issue 3 Pages 925-926
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Call Number Serial 2121
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Author Kacelnik, A.
Title R.C. Bolies and M.D. Beecher, Editors, Evolution and Learning, Lawrence Erlbaum, Hillsdale, New Jersey (1988), p. x Type Journal Article
Year 1990 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 40 Issue 3 Pages 602-603
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Call Number Serial 2119
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Author Cuthill, I.C.; Kacelnik, A.; Krebs, J.R.; Haccou, P.; Iwasa, Y.
Title Starlings exploiting patches: the effect of recent experience on foraging decisions Type Journal Article
Year 1990 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 40 Issue 4 Pages 625-640
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Abstract Laboratory and field experiments have shown that, as predicted by the marginal value model, starlings, Sturnus vulgaris, stay longer in a food patch when the average travel time between patches is long. A laboratory analogue of a patchy environment was used to investigate how starlings respond to rapidly fluctuating changes in travel time in order to find out the length of experience over which information is integrated. When there was a progressive increase in the amount of work required to obtain successive food items in a patch (experiment 1), birds consistently took more prey after long than after short travel times; travel experience before the most recent had no effect on the number of prey taken. Such behaviour does not maximize the rate of energy intake in this environment. The possibility that this is the result of a simple constraint on crop capacity is rejected as, when successive prey were equally easy to obtain up until a stepwise depletion of the patch (experiment 2), birds took equal numbers of prey per visit after long and short travel times: the rate-maximizing behaviour. A series of models are developed to suggest the possible constraints on optimal behaviour that affect starlings in the type of environment mimicked by experiment 1.
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Call Number Serial 2118
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Author Cuthill, I.; Kacelnik, A.
Title Central place foraging: a reappraisal of the `loading effect' Type Journal Article
Year 1990 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 40 Issue 6 Pages 1087-1101
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Abstract Animals that provision a central place usually bring back larger loads when foraging far from home. This positive correlation between average load size and distance is typically explained as rate-maximizing behaviour in the face of a trade-off between travel costs and a decelerating rate of prey gain in food patches (the `loading effect'). By using feeders to provide wild parent starlings, Sturnus vulgaris, with constant rates of prey loading, a positive load-distance correlation was shown to exist in the absence of a loading effect (experiment I). However, in a laboratory simulation where no load was transported (experiment II). the average number of prey eaten in patch visits by self-feeding starlings was invariant with travel distance, so the explanation of the load-distance correlation in experiment I must lie in featues peculiar to central place foraging. Bottlenecks in ingestion by chicks and interruption by visual detection of nest disturbance (experiment III) were rejected as causes of the correlation. Risks of dropping prey in flight appeared low, but the risk of kleptoparasitism received weak support. The travel-load size correlation may be an adaptive response to load transport costs, as return travel times increased with the load size being carried (experiment IV).
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Call Number Serial 2116
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Author Cassini, M.H.; Kacelnik, A.; Segura, E.T.
Title The tale of the screaming hairy armadillo, the guinea pig and the marginal value theorem Type Journal Article
Year 1990 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 39 Issue 6 Pages 1030-1050
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Abstract Foraging by screaming hairy armadillos, Chaetophractus vellerosus, and guinea pigs, Cavia porcellus, was studied in the laboratory. The main question was whether patch exploitation varies with overall capture rate as predicted by the marginal value theorem (MVT). Armadillos in experiment I and guinea pigs in experiment II experienced a single travel time between depleting patches of two kinds: good and poor. There were two treatments, which differed in the quality of poor patches. MVT predicts that within a treatment, more prey should be taken from good than from poor patches and between treatments, good patches should be exploited in inverse relation to the quality of poor patches and poor patches should be exploited in direct relation to their own quality. In experiment III, guinea pigs experienced three treatments which differed in the travel requirement, while the two patch types remained the same. MVT predicts that within a treatment more prey should be taken from good than from poor patches and that between treatments more prey should be taken from both patch types as travel requirement increases. The qualitative predictions were supported in the three experiments. The quantitative fit was good but there was a bias towards more severe patch exploitation than predicted. The results indicate that in these species patch exploitation depends on overall food availability as predicted by the MVT when overall food availability differs either because of patch type composition or because of differences in travel requirement between patches.
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Call Number Serial 2120
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Author Caraco, T.; Kacelnik, A.; Mesnick, N.; Smulewitz, M.
Title Short-term rate maximization when rewards and delays covary Type Journal Article
Year 1992 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 44 Issue Part 3 Pages 441-447
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Abstract In nature foragers must exploit resources that vary randomly in both the energy acquired per item (reward) and the time required to pursue, capture and process an item (delay). Furthermore, rewards and delays associated with particular resources may often covary significantly. An analytical model asks how variance-covariance levels for rewards and delays could influence choice of resources when lack of information or cognitive limitation implies that a consumer attempts to maximize its short-term rate of energy gain. Both greater expected reward and reduced expected delay clearly should enhance preference for a resource. The model predicts that increased delay variance and reduced reward-delay covariance should increase a forager's preference for a resource. A forager should be risk-averse towards reward variance when the reward-delay covariance is positive, but should become risk-prone towards reward variance when the reward-delay covariance is negative.
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Call Number Serial 2113
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Author Brunner, D.; Kacelnik, A.; Gibbon, J.
Title Optimal foraging and timing processes in the starling, Sturnus vulgaris: effect of inter-capture interval Type Journal Article
Year 1992 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 44 Issue 4 Pages 597-613
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Abstract Laboratory experiments with starlings, Sturnus vulgaris, were conducted to investigate the interaction between timing and cost-benefit considerations. The design simulated an environment in which food was distributed in patches. Patches contained a random number of food items (N=0-4) separated by a fixed inter-capture interval or fixed interval. All patches ended with sudden depletion. The time elapsed since the last prey capture was the only way to detect the depletion of the patch. Once the patch was depleted a new patch could be reached by travelling between two perches. Three measures of timing were taken: (1) rate of working for food as function of `waiting' time in a patch, (2) the time of the last response in a patch or `giving-in' time, and (3) the time at which travel was initiated or `moving-on' time. The fixed interval that characterized patches was varied between conditions. The mean time of the peak in working rate was consistently centred around the fixed interval, while the other two measures of timing kept a roughly linear relation to the fixed interval, with slope greater than one. In accordance with Scalar Expectancy Theory, variability in the three forms of timing was proportional to the magnitude of the fixed interval. The birds seemed to take account of this increase in variability as shown by the mean value of their giving-up criterion. These results imply that information-processing constraints are important for modelling behavioural optimality.
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Call Number Serial 2112
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Author Beauchamp, G.; Kacelnik, A.
Title Effects of the knowledge of partners on learning rates in zebra finches Taeniopygia guttata Type Journal Article
Year 1991 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 41 Issue 2 Pages 247-253
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Abstract Many interpretations of the adaptive value of group living involve tranfer of knowledge. However, according to learning theory, being in a pair with a knowledgeable partner can have paradoxical consequences. Obtaining food by following a skilled companion may reduce the ability of naive individuals to learn about clues that signal the occurrence of food. This study examined the relation between learning and following in paris of zebra finches. Knowledgeable partners were trained to obtain food from a computer-controlled dispenser by using the information provided by a signal. For non-knowledgeable partners, the signal was irrelevant and could not be used to predict foraging opportunities. The rate of learning about the signal by naive birds that shared the experience of either knowledgeable or nonknowledgeable tutors was then examined. Naive birds learned more slowly as a result of being in a pair with a knowledgeable than a non-knowledgeable partner. Well-informed mates acted as a reliable cue to predict foraging opportunities, and thus overshadowed the independent signal. The knowledge of a partner influences learning rates in naive individuals, but in the opposite direction to that predicted by earlier accounts of learning in social contexts.
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Call Number Serial 2115
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Author Bateson, M.; Kacelnik, A.
Title Accuracy of memory for amount in the foraging starling,Sturnus vulgaris Type Journal Article
Year 1995 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.
Volume 50 Issue 2 Pages 431-443
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Abstract Attempts to include psychological constraints in models of foraging behaviour differ in their assumptions concerning the accuracy of estimation of environmental parameters. Psychologists model estimation error as increasing linearly with the magnitude of a stimulus (Weber's Law), whereas behavioural ecologists either ignore error or assume it to be independent of stimulus magnitude. Studies on the estimation of time intervals have confirmed Weber's Law, but there are few data on the accuracy of estimation of amounts of food. Since the currency of most foraging models is the amount of food acquired per unit of time spent foraging, information on estimation of amount is required. Here, a titration method was used in which starlings chose between two cues. One colour signalled a standard food reward, and the other a reward that adjusted in magnitude according to the birds' choices: it increased when the standard was preferred and decreased when the adjusting option was preferred. There were two standards of 3 and 9 units of food, each of which was delivered at two rates to control for possible effects of rate of reinforcement on discrimination. The observed value of the adjusting option oscillated around a mean value slightly larger than that of the standard. The amplitude and period of these oscillations were larger when the standard was larger, independent of the rate of reinforcement. Also, molecular analysis showed that the probability of choosing the currently larger alternative increased as the relative difference between the adjusting option and standard increased. These results are consistent with Weber's Law applying to starlings' memories for amounts of food.
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Call Number Serial 2110
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