Corvid Researcher Claudia Wascher

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Written By Animalcognition

Claudia Wascher is a behavioral biologist and postdoctoral researcher at the University of Valladolid, Spain. Her work is centered on corvid cognition and corvid intelligence. If you would like to learn more about her current work and past publications, please visit her website.


1: Your current research focuses on social cognition, cooperation, and vocal communication in corvids. What led you to study these subjects and these animals?

A: Corvids are very fascinating study subjects. My main study species, the carrion crow, lives in a flexible social system. In most European populations crows breed in territorial pairs, but in a population in Northern Spain, due to environmental factors, cooperative breeding occurs. This means not only the parents care for the offspring, but also ‘helpers’ provision for the nestlings. Enhanced cognitive skills are assumed to help individuals to deal with the challenges of group living. Carrion crows, which show a flexible social system, are an ideal model system for the study of cognitive abilities. Certain forms of cooperation for example, require certain cognitive skills. Individuals need to know who their cooperation partners are, how much they are investing, and they need to be able to wait for a future return. In our research we could show that carrion crows and common ravens do possess these cognitive abilities, which allows them to engage in complex cooperative interactions.


2: In one of your most recent studies, you discovered that carrion crows can remember if another crow is reliable or not, and that they will often ignore the calls of crows who have proven to be unreliable in the past. How did you determine this?1

A: We performed a study where we played back alert calls of four different conspecifics (other crows), which the test subjects did not know before. In an initial association phase we paired the calls of one ‘reliable’ crow with a visual cue of danger (dead conspecific), whereas the calls of other ‘unreliable’ crows were not paired with a visual cue. In a consecutive test phase we were interested whether or not the crows responded differently to the playbacks of ‘reliable’ or ‘unreliable’ model individuals. We therefore coded the focal crows’ attention and vocal behaviour. We did not find any significant differences in attention behaviour, which could be explained by the kind of calls we used. It makes sense that the focal crows did not approach the alert calls of a conspecific, which signals danger. However, we did find differences in the frequency of calls they made. Crows decreased their own calling in sessions where the reliable model was played back. We think that this response shows the crows decreasing their own calling in order not to miss any information from the model individual in response to the reliable crow.


Crows Socializing, corvid intelligence

3: After conducting a series of experiments, you were able to detect a correlation between how well individual corvids performed in cognitive tests, and their social behaviors. What is the correlation?2

A: Presently we have a lot of empirical evidence for enhanced cognitive abilities in different social mammalian, bird and also fish species. We do think that these cognitive skills evolved in the social context in order to help individuals to deal with social challenges. However, many of these cognitive skills could also have evolved in a foraging or mating context, and, therefore, we need empirical evidence showing that enhanced cognitive skills are actually used in social contexts. In my study I provide the first empirical evidence that individuals performing well in cognitive tasks also more frequently engage in social behaviours, for example, approaching each other and affiliative behaviours. The present study is a first effort at providing empirical support for the assumption that cognitive skills evolved in the context of social challenges by linking individual performances in socio-cognitive tasks and social behaviour within the group.


4: In parrots, social behavior seems to also have correlations to intelligence.3 Do you think that this correlation might be a common phenomenon in other species as well, avian and otherwise?

A: Yes indeed. It is of scientific interest to ask similar questions regarding the evolution of advanced cognitive skills in different species living in complex social systems. This way, interesting similarities regarding cognitive skills can be found in various mammalian, bird and fish species.


5: Some of your past work has also involved geese. You found that they experience stress when they observe some social encounters. Could you tell us more about these findings, and their implications?4

A: We investigated heart rate modulation by social contexts in greylag geese. We found that social interactions, for example, aggressive encounters, were amongst the most potent modulators of the physiological stress response. Importantly, this activation of the stress response is not necessarily a negative thing, an increase in heart rate might help an individual to cope with a given challenge and prepare for action. Interestingly, it was not only active involvement in interactions, which modulated heart rate, but merely watching social interactions increased the heart rate in geese that were bystanders. This heart rate increase in bystanding geese was higher when affiliated individuals (partner, family members) were involved in the interaction, which is indicative of emotional involvement.


Cawing Crow, corvid intelligence6: Can you tell us a bit about any research projects you are currently conducting?

A: Presently I’m further investigating vocal communication in carrion crows. Over a time course of five years I recorded calling behaviour in two populations of captive carrion crows, one in Austria and one in Spain. In both populations we found more than 20 different call-types and variations of call-types; around 8 of these calls were recorded in both populations, the rest of the calls differed between populations. I’m now investigating whether cooperative breeding modulates vocal behaviour. From our preliminary data it seems that although both populations show approximately the same amount of different call types, each individual uses more call-types in the Spanish compared to the Austrian population. Further, Spanish crows are calling more frequently. This could be due to larger group sizes in the Spanish crows, and therefore more individuals need to stay in contact and coordinate their actions. I’m also interested in the context in which these different call types are shown.


7: Have you been able to link call-types to any specific contexts so far?

A: This is ongoing work. What we know so far is that crows do show individual call repertoires, so different individuals using different calls. There are several call types which are used in a specific context, such as an alarm or aggressive context, but there are also call types which are used in different contexts, e.g. as contact calls but also in a territorial context.


Claudia Wascher with Crows, studying corvid intelligence

8: What was one of your most incredible moments in the field?

A:  There are so many it is hard to think about a single one. Performing cognitive experiments in captive crows is great fun because the crows really like to participate, at least on most days. It is fascinating to see how crows behave in different test situations and also how different individuals deal with these cognitive challenges.

In the field, spring is very exciting, when young crow fledglings leave the nest and start exploring the world. It is really funny how ‘stupid’ young crows are in their first months. They sit on the street and the parents really need to take good care and need to warn them of danger. During this time young crows also seem to have a lot of fun hanging in trees upside down, or singing in order to practicing their communicative skills.

9: What fact about corvid cognition or behavior do you think is most important for the world to know?

A: Corvids are a big family of more than 120 different species with great plasticity in their social system. This makes them ideal study subjects to investigate how cognitive skills evolved depending on the social system. Understanding under which circumstances behaviours evolved in corvids is important because it will give us insight into a potential convergent evolution of enhanced cognitive skills in distantly related taxa (mammals and birds) living under similar social and environmental circumstances.


Videos of experiments



From the recent reliability experiment. In the central room of the aviary (behind the wall) we played back calls of unknown conspecifics, which we randomly assigned to a “reliable” or “unreliable” role. The focal individuals could then peek through small holes in the wall in order to gain visual access into the central room, which is also seen in the video. In our experiment we did not find this kind of attention behaviour to be significantly affected by reliability of the model individual, however, the frequency of vocalisations of the focal individuals was significantly lower when reliable model individuals were played back compared to test sessions with unreliable models played back. We interpret the decrease in calling after hearing a reliable alert call as an attempt to gain as much auditive information as possible from reliable but not unreliable model individuals.



From the inequity experiment.5 Crows were tested in dyads and one partner was treated unequally to its disadvantage, receiving a less preferred reward (grape) for an exchange compared to an experimental partner who received cheese. In this condition, crows significantly more often refused to take the reward, which means they actually successfully completed the exchange (did the work) but refused to take the reward, compared to other test conditions. This indicates that crows and ravens are sensitive to unequal treatment. In the video Peter refuses to take the grape after successfully exchanging the initial item.



From the Hillemann et al. 2014 Animal Behaviour study. The crow Peter waits for 40 sec in order to exchange a low quality food item with more preferred food.



From the Hillemann et al. 2014 Animal Behaviour study. Resa waits in order to exchange one piece of food against more pieces of the same reward. However, this is what the crows and ravens generally do NOT do, they wait in order to optimize quality but not quantity.


This interview was conducted by Amanda Pachniewska, founder & editor of Animal Cognition. 


1 – Claudia Wascher, Friederike Hillemann, et al.
Carrion Crows Learn to Discriminate Between Calls of Reliable and Unreliable Conspecifics
Animal Cognition

2 – Claudia Wascher
Individual Performance in Socio-Cognitive Tasks Predicts Social Behavior in Carrion Crows

3 – Social Complexity Gives Parrots Big Brains

4 – Claudia Wascher, et al.
Heart Rate Responses to Agonistic Encounters in Greylag Geese, Anser anser
Animal Behaviour

5 – Friederike Hillemann, et al.
Waiting for Better, Not More: Corvids Respond to Quality in Two Delay Maintenance Tasks
Animal Behaviour