Theory of mind refers to the ability to attribute mental states to others and to predict their behaviour based on inferences about their mental states, for example their perception, desires, or beliefs. Forty years ago, research on theory of mind originated from the question of whether or not chimpanzees (Pan troglodytes) have a theory of mind, a question that – after all this time – is still debated. In the present thesis, I investigate theory of mind and its precursors in birds of the crow family, specifically Eurasian jays (Garrulus glandarius), California scrub-jays (Aphelocoma californica), and carrion crows (Corvus corone corone). Corvids have been reported to possess theory of mind-like abilities. This qualification reflects the fact that most research on theory of mind in these birds has revolved around the ability to respond to perceptual and desire states of conspecifics, and so far has not produced evidence for or against an ability to also respond to others’ beliefs. Further, it is unclear which mechanisms could be the basis of corvids’ abilities. Thus, there are two open questions in regard to corvid theory of mind my thesis aims to address. To address these questions, first, I investigated the ability of Eurasian jays to respond to the false belief of a conspecific in a caching paradigm, where the knowledge of a conspecific observer about the accessibility of two caching sites was manipulated (Chapter 2). In Chapter 3 I explore which behavioural cues might present the basis of the jays’ ability to respond to the desire of a conspecific in a caching context. In Chapter 4, I report a study on biological motion perception in scrub-jays, a phenomenon suggested to be crucial for the detection of social agents. In Chapter 5, I assess scrub-jays’ sensitivity to gaze of a human and a conspecific. Finally, in Chapter 6, I report a study investigating the face inversion effect in carrion crows, an effect that is indicative of a ‘special’ relevance of faces. I conclude by discussing how the presented studies could help us inform our understanding of corvid theory of mind-like abilities.

The family Corivdae, which includes crows and ravens, contains arguably some of the most intelligent species the animal kingdom has to offer. Separated from primates by at least 252 million years of evolution, birds bear striking physiological differences from mammals, while displaying similar intellectual abilities. This apparent convergent evolution of intelligence sheds light on what could possibly be a universal phenomenon. While many excellent studies show the abilities of corvids, the majority of them test only captive subjects. This study tested the capabilities of both captive and wild ravens, from three different species. The first portion of the study tested which of the four solutions offered wild ravens would choose when solving a Multi-Access Box. The second portion of the study tested the performance of wild and captive ravens when solving a Multi-Latch Box. The nine raven subjects were split into four different levels of enculturation based on their known histories. Two wild common ravens (Corvus corax) on the campus of the University of Arizona were level 1, four wild common ravens in the parking lot of a United States Forest Service parking lot were level 2, two captive and trained Chihuahuan ravens (Corvus cryptoleucus) from the Raptor Free Flight program at the Arizona-Sonora Desert Museum comprised level 3, and one captive and trained white-necked raven (Corvus albicollis) made level 4. It is possible to run trials with completely wild and free birds. It was found that ravens prefer direct methods of obtaining food, such as opening doors and pulling strings, instead of tool use. It was also found that while the relationship between enculturation level and success solving a puzzle was not linear, captive birds were the best solvers. The data given here suggest that captivity, training and enrichment history, and enculturation should all be considered when performing cognitive studies with animals.

The present thesis examined whether the corvid, Clark’s nutcracker, is able to discriminate knowledge states between human experimenters based upon gestural cues using an object-choice task. To do so, the knowledge state of two experimenters was manipulated – one experimenter was informed, and the other uninformed, as to the location of a hidden food reward. To find the reward, the birds had to use the gesture of the informed experimenter and refrain from using the unreliable gesture of the uninformed experimenter. The nutcrackers responded to the gesture of the informed experimenter at above chance levels when simultaneously presented with the uninformed experimenter’s gesture. When the uninformed experimenter’s gesture was presented alone, the birds continued to follow the gesture. These results suggest the birds learned the gesture was meaningful, perhaps by associative learning, yet when this mechanism was not reliable the nutcrackers based their choices on the knowledge states of the experimenters.

The present thesis examined whether the corvid, Clark’s nutcracker, is able to discriminate knowledge states between human experimenters based upon gestural cues using an object-choice task. To do so, the knowledge state of two experimenters was manipulated – one experimenter was informed, and the other uninformed, as to the location of a hidden food reward. To find the reward, the birds had to use the gesture of the informed experimenter and refrain from using the unreliable gesture of the uninformed experimenter. The nutcrackers responded to the gesture of the informed experimenter at above chance levels when simultaneously presented with the uninformed experimenter’s gesture. When the uninformed experimenter’s gesture was presented alone, the birds continued to follow the gesture. These results suggest the birds learned the gesture was meaningful, perhaps by associative learning, yet when this mechanism was not reliable the nutcrackers based their choices on the knowledge states of the experimenters.

Tool-use and tool-manufacture are thought to require high cognitive skills and have been considered as an exclusive attribute to primates. Recent observations of New Caledonian crows (NCCs) challenge this assumption. In this study 13 NCCs were tested with two different tool production tasks. The NCC either had to straighten a hook or bend a stick to retrieve food from two different kinds of tree trunks. The result showed that 3/5 birds bent sticks and used them to retrieve food and 1/5 birds straightened hooks to retrieve food. The birds managed to solve both tasks but not the birds in the control group. This indicates that NCC's tool making is a flexible innovative act and not just an innate predisposition to bend flexible material. This finding is interesting given that recent studies on human children show that below 8 years of age children fail in similar innovative tool making tasks.

In previous studies with stuffed dummies, we found interesting difference in nest defence of Red-Backed Shrike (Lanius collurio) against two similar nest predators: Jay (Garrulus glandarius) and Magpie (Pica pica). Jay was attacked very intensively, whereas Magpie almost wasn´t hited and Shrikes seemed to keep in cover. Here, I describe the antipredation behavior of the Red Backed Shrike against another stuffed corvids presented closely to Shrikes nests: Jay (Garrulus glandarius), Common Nutcracker (Nucifraga caryocatactes), Rook (Corvus frugilegus), Crow (Corvus corone) and Raven (Corvus corax). I found Jay and Nutcracker to be attacked by Shrikes very strongly, whereas Rook, Crow and Raven were attacked rarely (Shrikes only flied around them or sit at a distance, watching the dummy, sometimes accompanied with alarm-calls). Shrikes response is affected mainly by kind of predator, by age of youngs and by quality of concealment of nest. More - www.mn.ic.cz

Dans le règne animal, certaines espèces présentent une organisation en groupe complexe, permettant l’établissement d’interactions sociales plus ou moins élaborées entre les individus. Les comportements prosociaux, visant à améliorer le bien-être de l’autre, apparaissent préférentiellement entre animaux qui partagent une grande affinité ; ces comportements sont probablement favorisés par l’empathie, suggérant une prise en compte émotionnelle du partenaire. Les oiseaux, et particulièrement les corvidés et les psittacidés, se révèlent être d’excellents modèles pour étudier ce lien entre relation sociale et prise en compte de l’autre: ils forment des couples monogames sur le long terme au sein desquels une forte coopération existe. L’objectif de cette thèse est d’explorer comment le lien entre individus (familial, sexuel, amical) module les comportements prosociaux et empathiques. Les réactions des sujets sont évaluées via le partage de nourriture ou bien en observant une sensibilité accrue envers un congénère. Chez les perruches calopsittes (Nymphicus hollandicus), les oiseaux réagissent plus fortement au cri de détresse d’un oiseau préféré qu’au cri d’un autre congénère familier et les individus apparentés (frères et sœurs) partagent davantage la nourriture entre eux qu’avec les autres. Les perroquetsont tendance à être prosociaux mais la prise en compte de l’autre reste à confirmer. Les choucas des tours (Corvus monedula), placés dans une situation nouvelle avec un autre oiseau, passent plus de temps à proximité de leur partenaire sexuel que d’un autre oiseau de sexe opposé. Ces différents résultats suggèrent qu’un lien d’affinité existe entre les individus et qu’il façonne leurs comportements en termes de prosocialité et d’empathie. / In the animal kingdom some species form complex social groups in which elaborated relationships between individuals occur. Prosocial behaviors, i.e. actions that benefit others, preferentially occur between closely affiliated individuals and may be driven by empathy, the ability to identify and share the emotional states of others. Birds, particularly corvids and parrots, are excellent candidates for investigating the link between social relationship and other-regarding behavior. They are long-lived and form long-term monogamous pair-bonds in which a high level of cooperation is seen throughout the year. The aim of this thesis is to study how the nature of a relationship (sibling, mate or friend) can modulate prosocial behavior and its underlying emotions in parrots and a corvid species. The approach was to study food-sharing or behavioral reactions to stressful situations such as distress call playback or exposure to novel objects, in different social contexts. Cockatiels (Nymphicus hollandicus) reacted more to the distress calls of a closely affiliated partner than to those of a non-partner, and they preferably shared food with affiliated, related individuals. Different species of parrots preferentially chose a prosocial option over a selfish one, but it remains unclear whether they took the other’s perspective into account. Confronted with intimidating novel objects, jackdaws (Corvus monedula) spent more time in mutual proximity when paired with their mate than when with a familiar opposite-sex non-partner. However, they were not bolder when accompanied by their mate compared to a non-partner. These results suggest that an emotional link exists between affiliated individuals and that this special bond drives their prosocial and empathic behavioral responses. / Im Tierreich gibt es Arten mit komplexer Gruppenstruktur, in denen Individuen aufwendige soziale Beziehungen mit Artgenossen eingehen. Prosoziales Verhalten, ein Verhalten zum Wohle Anderer, tritt bevorzugt zwischen Individuen auf, die eine starke gegenseitige Bindung aufweisen. Prosozialität beruht auf Empathie-Fähigkeit, die wiederum ein gewisses Verständnis der emotionalen Lage von Artgenossen voraussetzt. Vögel, insbesondere Papageien und Krähen, sind geeignete Modelle, um Zusammenhänge zwischen sozialer Bindung und prosozialem Verhalten zu untersuchen: sie bilden Langzeit-monogame Paare, die das Jahr hindurch miteinander kooperieren. Ziel dieser Doktorarbeit ist es, herauszufinden, wie soziale Bindungen (verwandtschaftlicher, sexueller, oder freundschaftlicher Natur) prosoziales Verhalten und Empathie beeinflussen. Zu diesem Ziel wurden Studien über Futterteilen und Verhaltensreaktionen auf Stress in verschiedenen sozialen Kontexten durchgeführt. Nymphensittiche (Nymphicus hollandicus) reagierten stärker auf Warnrufe ihres Partners als auf die eines anderen Gruppenmitglieds. Ebenso teilten verwandte Sittiche häufiger Futter miteinander als mit anderen Individuen. Verschiedene Papageienarten bevorzugten in einer Entscheidungssituation prosoziale über egoistische Optionen, wobei unklar bleibt, ob sie die Perspektive ihres Partners verstanden. Dohlen (Corvus monedula), die mit einem für sie unheimlichen neuen Objekt konfrontiert wurden, verbrachten mehr Zeit in gegenseitiger Nähe, wenn sie mit Ihrem Partner als mit einem anderen Individuum getestet wurden. Sie verhielten sich aber in Gegenwart ihres Partners nicht mutiger. Die Ergebnisse legen nahe, dass Bindungen zwischen Individuen prosoziales Verhalten und empathische Reaktionen aufeinander beeinflussen.

Chez les oiseaux, les espèces aux aptitudes cognitives avancées, et celles faisant face aux coûts et aux bénéfices de la vie en groupe, sont particulièrement intéressantes pour étudier l'émergence de formes complexes de socialité. Dans ma thèse, j'ai étudié les mécanismes comportementaux sous-jacents à la diversité et la dynamique des relations sociales dans un groupe de corbeaux freux captifs, une espèce de corvidé monogame et coloniale. J'ai montré que les freux peuvent former des relations en dehors du contexte reproducteur et changer de partenaire au cours de leur vie. De plus, j'ai montré : une certaine résilience de la structure sociale face aux variations temporelles des relations, de la composition du groupe et du sex-ratio; et l’absence d’effets stabilisateurs des relations de dominance sur la structure. Mon travail démontre que la structure sociale chez le corbeau freux est plus qu’un simple agrégat de paires, et forme la base d’une organisation sociale aux multiples niveaux. / Numerous avian species are good candidates to study the emergence of complex forms of sociality, in particular the species showing advanced cognitive skills, and the one living in groups all year long, coping with the costs and benefits of group living. In my thesis, I investigated the proximate mechanisms underlying the diversity and dynamic of social relationships in captive adult rooks, a colonial and monogamous corvid species. I found that rooks have the ability to form non-reproductive social bonds and several pair bonds throughout their life. In addition, I found: that the group social structure was flexible enough to allow temporal variations of relationships, group composition and sex-ratio; and that dominance relationships do not have any long lasting effects on the stabilisation of the structure. Overall, my work demonstrates that rooks social structure extends far beyond a simple aggregation of reproductive pairs, and may be acknowledged as a multi-level social organisation.