Experimental assessment of problem solving by <Emphasis Type="Italic">Milvago chimango </Emphasis>(Aves: Falconiformes)

We report a preliminary assessment of problem solving as an estimate of behavioural innovation and learning ability of a generalist and abundant raptor, Milvago chimango, under controlled conditions in aviaries. Experimental tests consisted in presentation of a Plexiglas box with four lids leading to isolated pieces of meat. We recorded time to first contact with the box and time from this first contact to gaining access to the pieces of meat. We recorded the number of attempts to open the box and reach the first portion of meat, and the total number of lids opened by each individual during five successive daily sessions. We found that individuals of M. chimango quickly approached and made contact with the Plexiglas box, and responded successfully to the novel feeding problem of reaching the food inside. In our study, performance of individuals was enhanced after solution of the novel task for the first time, as indicated by the progressively reduced time taken to access the food. Further, some individuals gained access to an increasing number of sections of the Plexiglas box during subsequent sessions, suggesting significant learning ability. Our results indicated M. chimango has a remarkable ability to obtain food in a novel situation, an observation that agrees with anecdotal reports of opening of receptacles to obtain food in urban environments. The results support the idea of behavioural plasticity in this species.     

Social learning in common ravens, Corvus corax

We conducted an experiment to investigate whether the presence of a conspecific model can promote the acquisition of a motor task in common ravens. For this purpose, dyads, either of control birds or of model-observer pairings, were allowed to operate together in an arena with a set of identical boxes. Each box consisted of two compartments each containing a reward of three pieces of meat. The compartments were closed by gliding lids with red flaps on their front, opening horizontally in opposite directions. Naive control individuals opened the lids exclusively by levering, that is, jumping on top of the box, inserting the beak at the posterior rim of the lid and pushing it open. Models were trained to demonstrate an alternative opening technique, pulling at the front flap, then jumping on top of the box to get at the reward. In contrast to the control birds, observers initially opened boxes both ways, by pulling and levering. Furthermore, observers approached the boxes more quickly and showed less fearful behaviour than the control birds, which we attribute to the enhancing effect of the model. We discuss both stimulus enhancement and motor imitation as possible learning mechanisms. Even though observers initially obtained a considerable amount of reward produced by the models, scrounging evidently did not inhibit learning. Copyright 1999 The Association for the Study of Animal Behaviour.     

Testing for imitative and nonimitative social learning in the budgerigar using a two-object/two-action test

Male and female juvenile budgerigars, Melopsittacus undulatus, were allowed to observe a conspecific demonstrator using its beak to remove one of two distinctively coloured objects (i.e. a blue and a black stopper) from a hole in the lid of a box and eating seed from within. Both objects could be removed by either pulling up or pushing down. When subsequently allowed access to both stoppers, and rewarded with food for all removal responses, regardless of the object to which they were made and their direction, observer birds removed both stoppers in the same direction as their demonstrator. This effect was present on the first occasion when observers removed a stopper, and persisted over at least 24 trials. Female observers made more removal responses than males, but conspecific observation had equivalent effects on direction of responding in males and females. All observers tended to approach the same object as their demonstrator when the objects were discriminable using both spatial and colour cues, but not when they differed in colour alone. Contrary to previous findings, these results suggest that robust behavioural matching effects can be obtained in budgerigars, and that these birds are capable of motor imitation or emulation. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Cultural Diffusion of a Novel Food-finding Behaviour in Urban Pigeons: an Experimental Field Test

The cultural diffusion of a novel food-finding behaviour, piercing the paper cover of a box containing seed, was experimentally provoked in two flocks of pigeons (Columba livia): a closed aviary flock and an open urban flock. In the urban flock, piercing behaviour spread to 24 previously naive individuals. The rate of cultural diffusion was more rapid in the urban flock than in the aviary. In both situations, many individuals simply fed from the discoveries of birds that pierced, but this effect slowed diffusion less in the open urban flock because experienced piercers left the flock and naive birds entered it. Individual trial-and-error learning and natural shaping can be ruled out as mechanisms of diffusion in the present case.     

Stimulus enhancement in greylag geese: socially mediated learning of an operant task

We recently observed the spreading of a novel tradition in a flock of semiferal greylag geese, Anser anser: an increasing number of individuals began to bite and chew the stems of butterbur, Petasites hybridus. Because this behaviour spread particularly fast within families, social learning seemed to be involved. We therefore designed an experiment with hand-reared goslings, which were socially imprinted on humans, to investigate whether and how the observation of an experienced tutor affects the acquisition of a novel skill. Goslings had to open the gliding lid of a box to get at a food reward. To each of seven hand-reared observers a human tutor demonstrated where and how to open the lid, whereas seven controls remained untutored. All observers learned to perform the task but only one of the controls succeeded. The observers explored more often at the position shown by the tutor than elsewhere and seemingly learned by trial and error. In contrast, control birds explored primarily at positions that did not allow them to open the box. These results indicate that in greylag goslings the observation of an experienced model facilitates the learning of an operant task. We conclude that stimulus enhancement followed by operant conditioning were the mechanisms involved, which may have accounted for the fast spread of the stem-chewing tradition between family members. Copyright 2000 The Association for the Study of Animal Behaviour.     

The hindlimb myology of Milvago chimango (Polyborinae,Falconidae)

We describe the hindlimb myology of Milvago chimango. This member of the Falconidae: Polyborinae is a generalist and opportunist that can jump and run down prey on the ground, unlike Falconinae that hunt birds in flight and kill them by striking with its talons. Due to differences in the locomotion habits between the subfamilies, we hypothesized differences in their hindlimb myology. Gross dissections showed that the myology of M. chimango is concordant with that described of other falconids, except for the following differences: the m. flexor cruris medialis has one belly with a longitudinal division; the m. iliotibialis lateralis does not have a connection with the m. iliofibularis; the m. fibularis longus is strongly aponeurotic; the m. tibialis cranialis lacks an accessory tendons and the m. flexor hallucis longus has one place of origin, instead of two. The presence of the m. flexor cruris lateralis can be distinguished as it has been described absent for the Falconidae. We associated its presence with the predominant terrestrial habit of the M. chimango. Each muscle dissected was weighed and the relationship between flexors and extensors at each joint was assessed. The extensor muscles predominated in all joints in M. chimango. Among the flexors, the m. flexor hallucis longus was the heaviest, which could be related to the importance of the use of its talons to obtain food. J. Morphol. 274:1191–1201, 2013. © 2013 Wiley Periodicals, Inc.     

Socially biased learning among adult cottontop tamarins (Saguinus oedipus)

We presented adult cottontop tamarins (Saguinus oedipus) with a novel foraging task that had been used previously to examine socially biased learning of juvenile observers [Humle & Snowdon, Animal Behaviour 75:267–277, 2008]. The task could be solved in one of two ways, and thus allowed for an analysis of behavioral matching between an observer and a skilled demonstrator (trained to use one of the two methods exclusively). Because the demonstrator was an adult in both this study and the juvenile study, the influence of the observer's age could be isolated and examined, as well as the behavior of demonstrators toward observers of different ages. Our main goals were to (1) compare adults and juveniles acquiring the same task to identify how the age of the observer affects socially biased learning and (2) examine the relationship between socially biased learning and behavioral matching in adults. Although adults spent less time observing the trained demonstrators than did juveniles, the adults were more proficient at solving the task. Furthermore, even though observers did not overtly match the behavior of the demonstrator, observation remained an important factor in the success of these individuals. The findings suggested that adult observers could extract information needed to solve a novel foraging task without explicitly matching the behavior of the demonstrator. Adult observers begged much less than juveniles and demonstrators did not respond to begging from adult. Skill acquisition and the process of socially biased learning are, therefore, age‐dependent and are influenced by the behavioral interactions between observer and demonstrator. To what extent this holds true for other primates or animal species still needs to be more fully investigated and considered when designing experiments and interpreting results. Am. J. Primatol. 72:287–295, 2010. © 2009 Wiley‐Liss, Inc.     

Push or Pull: Imitation vs. Emulation in Great Apes and Human Children

All four species of great apes and young human children (12–24 mo of age) were administered an imitation task designed to distinguish between results learning (emulation) and action learning (imitation). Some subjects were exposed to a demonstrator either pushing or pulling a door to open a box, whereas others simply saw the door of the box opening itself in one of the two directions (the ghost control). Most of the apes successfully opened the box in both experimental conditions, as well as in a baseline condition, but without being influenced either by the demonstrator's actions or by the door's motions. In contrast, human children over 12 mo of age were influenced by the demonstration: the 18‐mo‐olds were influenced by the demonstrator's actions, and the 24‐mo‐olds were influenced both by the demonstrator's actions and by the door's motions in the ghost control. These results provide support for the hypothesis that human children have a greater propensity than great apes for focusing either on a demonstrator's action or on the result of their action, as needed, in social learning situations.     

Social learning influences the preferences of domestic hens for novel food

It has been argued that social learning helps animals either avoid noxious substances or identify food items, but evidence suggests that avian social learning is fundamentally different from that of mammals. In two experiments, we investigated whether the preferences of domestic hens, Gallus g. domesticus, for novel food were influenced by observing the feeding behaviour of conspecifics. In experiment 1, we attempted to confirm that birds can develop socially learnt aversions to unpalatable foods. Despite demonstrators showing a highly visible ‘disgust reaction’ after eating unpalatable coloured food, observers did not develop aversions to similarly coloured food. In experiment 2, we aimed to determine whether preferences for palatable food were socially learnt, and whether the extent of a demonstrator's preference for novel food affected the magnitude of the observer's socially learned preference. Demonstrators ate coloured food of standard or high palatability, or did not peck food at all. When the demonstrators pecked more frequently or fed more quickly from the food, the observers consumed a greater proportion of food of the same colour; however, this was only when the food was red, not green. We argue this indicates an unlearned aversion to red food, overcome by social learning of the food being highly palatable. The results provide no evidence that adult hens learn aversions through observing disgust reactions, but show that hens are sensitive to the extent of demonstrator preferences for palatable food. The data do not support the hypothesis that avian social learning is fundamentally different from that of mammals. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The Effect of Age and Sex on Object Exploration and Manipulative Behavior in a Neotropical Raptor,the Chimango Caracara,Milvago chimango

We studied object exploration and manipulative behavior in wild‐caught Chimango Caracaras (Milvago chimango), an opportunistic and generalist raptor species, in relation to age and sex differences. Each bird was presented with six objects. We then recorded the latencies to approach and first contact with the objects, the number of objects explored, and the number of exploration events performed on each object. Age influenced the tendency to explore in M. chimango. Compared with adults, juveniles were more likely to explore the objects, approaching and contacting them more quickly. The number of objects explored was also higher in young than adult birds. Both age classes used a variety of manipulative behaviors to explore the objects, some of which have been described as play in others studies. Sex did not affect an individual's likelihood to explore or the number and frequency of manipulative behaviors used during object exploration. The tendency for both young and adult birds to explore and manipulate objects that not resemble prey is likely to be a distinct advantage for a generalist species like M. chimango which must cope with a high diversity of modified environments.     

Social Learning of a Novel Foraging Skill by White-throated Magpie-jays (Calocitta formosa,Corvidae): a Field Experiment

The cooperatively breeding white-throated magpie-jay (Calocitta formosa) uses a variety of foraging tactics to find, harvest, and process food. Members of territorial groups forage together and may gain information about how to acquire food by observing each other. A field experiment was performed to determine whether a novel skill, door opening to gain access to food, was more rapidly acquired by members of groups in which a trained individual performed the skill. A higher proportion of jays in groups with behavioural ‘models’ (trained birds that opened doors in the presence of group members) acquired the door-opening skill than those groups without models. Young birds acquired the behaviour more frequently than older individuals. Aggressive behaviour at feeders may have affected the spread of the behaviour by reducing the likelihood that individuals performed the behaviour in the presence of other group members but may also have encouraged subordinate individuals to attempt door opening rather than ‘scrounge’.     

Behavioral Analysis of Social Effects on the Problem-Solving Ability in the House Mouse

The effects of the social context on the problem‐solving ability in the house mouse was evaluated by means of a puzzle box containing food, which could be opened by rotating a revolving door. The aim of the study was to clarify which mechanisms of social learning promote the acquisition of this complex motor skill. Young mice were exposed to the puzzle box in the presence of (i) demonstrators opening of the puzzle box; (ii) adults unable to open the puzzle box; and (iii) adults confined in one part of the cage and not manipulating the puzzle box. Results of the detailed analysis of the sequence of behaviors showed that (i) young mice successful in opening the puzzle box did not copy the sequence of actions performed by demonstrators; and (ii) the presence of adult conspecifics in proximity of the problem apparatus increased the rate of success of young mice. Results suggest that trial‐and‐error learning, social exposure and stimulus enhancement all play a role in the acquisition of the opening ability.     

The effects of demonstrator social status and prior foraging success on social learning in laying hens

Opportunities for social learning within a group of animals are likely to be influenced by the social dynamics of that group. Some individuals may be more influential demonstrators than others even when there are no differences in their skill level or performance. In this study of domestic hens, Gallus gallus domesticus, differences in demonstrator salience were examined. From 24 separate flocks we selected as demonstrators a dominant cockerel, a dominant hen, a mid-ranking hen or a subordinate hen. Demonstrators were pretrained to perform an operant discrimination task to obtain food. Six observers from each flock individually watched the demonstrator perform the task for four 5-min sessions held on consecutive days. On the fifth day observers were tested individually in the operant chamber. We analysed data from 19 flocks, where there were no quantitative differences in demonstrator performance. Observer hens of relatively high social status performed more correct operant pecks than observer hens of relatively low social status. Demonstrator category also had a significant effect on subsequent observer behaviour. Hens that had observed cockerels performed very few general pecks or operant pecks. Hens that had observed dominant hens performed more operant pecks, but hens that had observed sub-ordinate hens performed more general pecks in the chamber. The results suggested either that there was an interaction between dominance and gender in demonstrator salience or that dominant hens might have been influential because of some factor imperfectly associated with their dominance status. A possible candidate was the foraging ability of the dominant hens. In a second experiment using the same protocol, we manipulated the prior foraging success of dominant hens from four additional flocks but this had no significant effect on their subsequent influence as demonstrators. Copyright 1999 The Association for the Study of Animal Behaviour.     

Molecular systematics of the caracaras and allies (Falconidae: Polyborinae) inferred from mitochondrial and nuclear sequence data

The Polyborinae is the most diverse subfamily of the Falconidae in terms of both morphology and behaviour, and includes falconet‐shaped birds (Spiziapteryx), arboreal omnivores (Daptrius, Ibycter), as well as terrestrial generalists and scavengers (Caracara, Milvago and Phalcoboenus). The Polyborinae are endemic to the New World, with all but one species (Caracara cheriway) being restricted to Central and South America. Using over 7300 bp of mitochondrial and nuclear sequence data, we aim to clarify the taxonomy and biogeography of the Polyborinae. The genus Milvago was unexpectedly found to be polyphyletic, with Chimango Caracara Milvago chimango being related to the genus Phalcoboenus and Yellow‐headed Caracara Milvago chimachima being sister to Daptrius. Furthermore, very low genetic divergence was found among the four species of the genus Phalcoboenus, with the lowest divergence being between White‐throated Caracara Phalcoboenus albogularis and Mountain Caracara Phalcoboenus megalopterus. Our divergence time analyses revealed that the Polyborinae started to diversify in the Miocene, at about 14 Ma, and that the generalist/scavenger behaviour in the Falconidae appeared between 14 and 6.6 Ma. All speciation events within the caracaras occurred during the Pleistocene. This situation differs from the general pattern described for forest birds, in which most diversification events are older, occurring primarily in the Pliocene and Miocene.     

Simple Mechanisms Can Explain Social Learning in Domestic Dogs (Canis familiaris)

Recent studies have suggested that domestic dogs (Canis familiaris) engage in highly complex forms of social learning. Here, we critically assess the potential mechanisms underlying social learning in dogs using two problem‐solving tasks. In a classical detour task, the test dogs benefited from observing a demonstrator walking around a fence to obtain a reward. However, even inexperienced dogs did not show a preference for passing the fence at the same end as the demonstrator. Furthermore, dogs did not need to observe a complete demonstration by a human demonstrator to pass the task. Instead, they were just as successful in solving the problem after seeing a partial demonstration by an object passing by at the end of the fence. In contrast to earlier findings, our results suggest that stimulus enhancement (or affordance learning) might be a powerful social learning mechanism used by dogs to solve such detour problems. In the second task, we examined whether naïve dogs copy actions to solve an instrumental problem. After controlling for stimulus enhancement and other forms of social influence (e.g. social facilitation and observational conditioning), we found that dogs’ problem solving was not influenced by witnessing a skilful demonstrator (either an unknown human, a conspecific or the dog’s owner). Together, these results add to evidence suggesting that social learning may often be explained by relatively simple (but powerful) mechanisms.     

Effects of separation of resources on behaviour of high-, medium- and low-ranked hens in furnished cages

In our previous studies, we demonstrated that dominant hens had priority in using the dust bath, resulted in increased competition for the resource. It seemed that the problem was that the resource was placed on one side of the cage (‘localised’). Therefore, we designed a medium-sized furnished cage with a dust bath and nest box on both sides of the cage (‘separated’, MFS). To evaluate the effects of separation of these resources, we compared the behaviour of high-, medium- and low-ranked hens in MFS cage with that in small (SF) and medium furnished (MFL) cages with a localised resource. In total, 150 White Leghorn layers were used. At the age of 17 weeks, the hens were randomly divided into three groups and moved to small furnished cages (SF, 90 cm wide; five birds per cage) and two types of medium furnished cages (180 cm wide; 10 birds per cage) with a nest box and dust bath on both sides (MFS) and a nest box and dust bath on one side of the cage (MFL). The total dust bath and nest box areas per hen were same for the three cages. The dominance hierarchy was determined by observing the aggressive interactions and by this high-, medium- and low-ranked hens in each cage were identified. The behaviour, use of facilities and physical condition of these hens were measured. Data were analysed by using repeated measure ANOVA. A significant interaction between social order and cage design was found in the proportions of time spent in the dust bath and on performing dust-bathing (both P < 0.001), and these proportions tended to be higher in higher-ranked hens in SF and MFL. Conversely, the MFS low-ranked hens tended to use the dust bath more than the SF and MFL low-ranked hens. Thus, hens from each rank used the dust bath equally in MFS, though the MFS high-ranked hens tended to use the resource less than the SF and MFL high-ranked hens. While the frequency of pre-laying sitting was lower among low-ranked hens (P < 0.05), the proportion of time in the nest box was higher among low- than high-ranked hens (P < 0.01). The low-ranked hens spent more time performing escaping, moving and standing in the nest box. In conclusion, it is suggested that separation of the dust bath to two locations would be an effective arrangement to promote more equal usage of the dust bath by hens from each rank in the furnished cages. It was also confirmed in the present study that nest boxes were not only used for laying eggs but also as a refuge by lower ranked hens.     

Imitation of lever-pressing ‘strategies’ during the operant conditioning of albino rats

This experiment was carried out on ninety-one male Wistar rats in order to study the ability to learn by observation in an operant conditioning situation. All rats were trained on a ‘multiple’ schedule over twelve daily sessions. Four observer groups were constituted: One control group and three groups paired with demonstrator rats which used well-known and distinct lever-pressing ‘strategies’. During each session, 15 min of demonstration or simple presence of a naïve companion were followed by 30 min of training. It was shown that the rats which were paired with a demonstrator have a higher response rate than controls, but only during the first session. During the eleven following sessions, no significant differences could be observed between the four observer groups. Nevertheless, if we consider the percentage of utilization of the various ‘strategies’ by each rat, we can notice significant correlations between demonstrators and observers, during the last three sessions.     

Social learning directs feeding preferences in the zebra finch, Taeniopygia guttata

We tested sexually mature zebra finches to see whether social learning influenced their feeding preferences, in particular whether they followed the preference of a male or a female demonstrator, of a red-ringed or a green-ringed male, and of a familiar or an unfamiliar male. Each observer was exposed to two demonstrators feeding at different-coloured hoppers, and then tested with a choice of hoppers to see which of the two colours they preferred. Males showed no preference between male and female demonstrators when choosing from which colour of food hopper to feed, but females preferred to feed from the hopper colour the male demonstrator had used. Both males and females exposed to male demonstrators wearing red or green leg rings fed preferentially from the same colour hopper as the red-ringed demonstrators had used. Finally, male birds exposed to familiar and unfamiliar demonstrators, preferred the food hopper from which the familiar demonstrator had fed. We interpret the results as indicating differences between the demonstrators in the amount of attention they attracted from observers.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Obtaining accurate measurements of the size and volume of insects fed to nestlings from video recordings

Video recordings are commonly used to study the types, amount, and size of food items provided to nestling birds. However, the accuracy and repeatability of estimates of the size of food items from video recordings has not been examined. We assessed three aspects of the reliability of measuring prey size from video recordings of Great Tits (Parus major) provisioning nestlings. To test the accuracy of measurements of prey size (length and width) used to determine prey volume, we molded artificial plasticine caterpillars and compared their size and volume as determined using measurements of length and width on screenshots of video recordings (using the vertical diameter of nest‐box entrance holes as a size reference) to their actual size and volume. We also examined within‐ and among‐observer repeatability of measurements of the size and volume of actual prey items delivered to nestlings by adult Great Tits. We found that observers were able to accurately measure prey size and determine volume, with high agreement between the actual size and volume of plasticine caterpillars and the size and volume as determined from measurements made on screenshots from video recordings (r_ICC = 0.99). In addition, within‐ and among‐observer repeatability were also high (r_ICC = 0.98 and 0.93, respectively). Overall, our results suggest that the size of prey items delivered to nestlings by adults in video recordings can be accurately measured and those measurements, in turn, can be used to accurately determine the volume of those insect prey.