Crows: birdbrains or not
ABSTRACT
Crows and other corvids have throughout history been described in folktales and myths as intelligent birds, and in reason years more and more stories of human-crow interactions have surfaced on the internet. The aim here is to seek an answer to whether crows really are as intelligent as they often are depicted. Crows have been found to use tools, understand causality, and recognising ‘dangerous’ humans and passing on the information to other crows. It does appear that crows are as intelligent as they are portrayed.
I. INTRODUCTION
In Aesop’s fable the Crow and the Pitcher, the crow depicted is intelligent enough to understand, if it adds enough stones to the pitcher the water lever will rise sufficiently for it to get a drink (Jelbert et al., 2014). There are stories from the real world as well, where crows appear to act with higher cognitive functions. One case where this is evident is the story of the girl who receives gifts from the crows she has fed on a daily basis for four years (Sewall, 2015). Going though the internet, there are many stories of these human-crow interactions. The aim here is to see if there is a grain of truth to these stories, and find out whether crows really are as intelligent as some people claims. In other words, are crows birdbrains or not?
II. THEY ARE NO TOOLS
The New Caledonian crow has become infamous due to its tool making skills in the wild. An experiment performed by Taylor et al. (2007), found that not only are New Caledonian crows able to use tools, but also use what is known as a metatool (a tool used to extract or manufacture a second tool). In the experiment, seven New Caledonian crows where tasked with extracting a piece of meat from a box using a long stick. The crows were presented with two barred boxes; one with the long stick and one with a stone. The aim was for the crows to use a shorter stick (the metatool) to extract the long stick before they could extract the meat. Of the seven crows, six of them tried immediately to extract the long stick, and four of the crows successfully obtained the meat in the first trial. Taylor et al. (2007) argues that the crows didn’t solve the metatool task by trial-and-error, but by what is known as analogical reasoning, and this may explain why New Caledonian crows are so successful in manufacturing tools in the wild (Taylor et al., 2007).
Recently it has also come to light that another species of crows are capable of using tools; the wild-extinct, captive-only Hawaiian crow (Rutz et al., 2016). Rutz et al. (2016) experimented with 104 Hawaiian crows, and found that food extractions from vertical and horizontal crevices and horizontally drilled holes were completed within 60 seconds of probing time. They also noted that the crows regularly selected tools which befitted the specific situation; such as choosing the right dimensions, replaced unsuitable tools, and even manufacturing tools from plant materials. Even the naïve juveniles, raised separately without an opportunity to observe adult tool-using crows in action, eventually began using tools to probe for hidden food (Rutz et al., 2016).
III. AESOP’S FABLE COMES TO LIFE
Aesop’s fable mentioned in the beginning has given rise to a way of studying birds’ ability to understand causality, aptly named Aesop’s fable paradigm. In this experiment birds are tasked with dropping objects of different mass and material into a water filled tube, to raise the water level enough for the birds to reach the food floating on the surface (Jelbert et al., 2014). When tested on New Caledonias crows, Jelbert et al. (2014) found the crows preferred to drop sinking objects, objects which was solid, and they had a preference for tubes with a higher water level. This indicates the New Caledonian crows understand that different object affect the water level differently, and can therefore reason which objects would serve the better purpose (Jelbert et al., 2014). There are, however, limits to the crows understanding of causality, as the crows failed to attend to the width of the tubes. They failed as well in what Jelbert et al. (2014) describes as a ‘counter intuitive U-shape apparatus’, where there were three tubes in a line, and the middle tube was connected to only one of the outer tubes. The crows failed in realising that dropping objects in one of the outer tubes the water would rise in the middle tube (Jelbert et al., 2014). This understanding of causality and water displacement equals that of 5-7 year old children (Jelbert et al., 2014).
IV. STRANGER DANGER
Crows are not only capable of using and manufacturing tools and understand water displacement as well as a seven year old; they are also capable of recognising human faces. A five year study by Cornell et al. (2012) found, that American crows captured, while the captor wore a mask, were able to remember the mask and every time the crow saw the mask, it would begin scolding the person wearing the mask. Only 7-15 crows were originally captured and released, and when exposed to the mask, they immediately started scolding the ‘dangerous mask’, which indicates individual learning (Cornell et al., 2012). However, not only did the previously captured crows scold the mask, other crows would join in, forming mobs which would collectively scold the mask, with the occasional swooping. To begin with, the mobs consisted predominantly of the captured crows and the crows observing the initial capture, but later naïve lone crows would join the mobs as well. This behaviour indicates there is some form of social learning between groups of crows, so called horizontal social learning (Cornell et al., 2012). Lone adult crows were not the only once to learn of these ‘dangerous masks’. Young crows of the captured adults had also been conditioned by the parents to scold the ‘dangerous masks’, and could be observed to individually scold the masks when they observed them. This indicates a form of knowledge-transfer between generations (Cornell et al., 2012). The mob formation and socially learned scolding of the masks, had in the five year period doubled in frequency and spread for up to at least 1.2 km away from the original place of capture (Cornell et al., 2012).
V. CONCLUSION
Based on the evidence presented, it is clear that crows appear to possess high cognitive functions, enabling them to use and manufacture tools; understand causality and water displacement as well as any 5-7 year old human; and learn to recognise ‘dangerous’ human faces, and pass on the information to their off-spring and other crows who have not been directly exposed to the ‘dangerous’ humans. With all of this in mind, it seems there is some truth to the myths and stories of intelligent crows. Crows may possess a bird brain, but they are no birdbrains themselves.
REFERENCES
Cornell, H. N., Marzluff, J. M. & Pecoraro, S. 2012. Social learning spreads knowledge about dangerous humans among American crows. Proc. R. Soc. B 279: 499-508.
Jelbert, S. A., Taylor, A. H., Cheke, L. G., Clayton, N. S. & Gray, R. D. 2014. Using the Aesop’s fable paradigm to investigate causal understanding of water displacement by New Caledonian crows. PLoS ONE 9: e92895. DOI: 10.1371/journal.pone.0092895.
Rutz, C., Klump, B. C., Komarczyk, L., Leighton, R., Kramer, J., Wischnewski, S., Sugasawa, S., Morrissey, M. B., James, R., St Clair, J. J. H., Switzer, R. A. & Masuda B. M. 2016. Discovery of species-wide tool use in the Hawaiian crow. Nature 537. DOI: 10.1038/nature19103.
Sewall, K. 2015. The girl who gets gifts from birds. http://www.bbc.com/news/magazine-31604026. Acces-sed 4 October 2016.
Taylor, A. H., Hunt, G. R., Holzhaider, J. C. & Gray, R. D. 2007. Spontaneous metatool use by New Caledonian crows. Curr. Biol. 17: 1504-1507.
Recommended viewing: A Murder of Crows
