Why crows are not as birdbrained as we think
Crows can use tools, solve problems and remember who their friends and enemies are
FOR MANY years my only close contact with crows occurred while staying in my mother-in-law’s house in Tipperary. My clearest memory is of large flocks of extremely noisy birds intruding on my Saturday morning lie-in. They were just a general nuisance. More recently however, my respect for them has increased significantly as I’ve become intrigued with their impressive intelligence.
I generally eschew anecdotes as evidence, but two recent events illustrate their abilities to problem solve. In one case a friend threw some very stale bread rolls out into the back garden. A crow arrived and had great trouble breaking up the bread. It picked up a roll, walked to the end of the garden and dropped the bread into a water bowl, waited a minute or so, retrieved the bread and enjoyed its meal.
Another friend informed me that at her local golf club, crows have learned to unzip the pockets on golf bags to access the snacks and lunches of distracted golfers. They have also been recorded dropping tough nuts from overhead wires onto traffic crossings, waiting for the lights to change, and then retrieving nuts that have been crushed by cars.
A lot of formal research has been done on the intelligence of crows and they are regarded as some of the brightest performers in the avian world. A star among stars is the New Caledonian crow that utilises a wide range of tools in foraging for food. For example, it forms hooks from twigs in order to snare insects and step-cuts tough leaves with which to dig. These tools are carried about by the birds on hunting missions.
One New Caledonian crow in captivity was observed to bend a straight piece of wire into a hook in order to retrieve a piece of meat from a tube. Since then, this behaviour has also been demonstrated in rooks. The rooks were also able to select an appropriately-sized stone from an array in order to use it to free a worm from a tube with a trap door at the bottom. The stone had to be just the right size to accomplish the task.
Crows and rooks belong to a large family of birds called corvids. There are more than 120 species of corvid that also include choughs, ravens, jackdaws, jays and magpies.
Magpies have been shown to recognise themselves in tests using mirrors. The birds were marked with a yellow spot that could not be seen except in the mirror. When they saw their reflection they attempted to access the mark on their bodies with their beak or foot.
Jays and other members of the corvid family will hide large quantities of food in a variety of locations for times when food is scarce. They can remember large numbers of cache sites over periods of months. They will steal from the caches of other birds and if they notice that they are observed while hiding their food, will return later and relocate it.
Crows presented with beakers of water containing floating food that is out of reach of their beaks will drop stones into the beaker, raising the water level to a point where they can reach it.
There are a number of factors that contribute to the impressive intelligence of corvids. They are relatively large brained, having a brain-to-body weight ratio similar to that of the great apes. They are also very sociable birds and look after their young for an extensive period of time. They are generally co-operative brooders and the young have lots of learning opportunities with extended group members as well as with their parents.
Crows are also reported to recognise and remember human faces. A group of researchers at a US university were involved in netting and ringing crows. Students involved in the ringing were mobbed by the crows over the following weeks. They left college on vacation and upon their return were again subjected to mobbing. Some students who had left the college were reportedly remembered even years later.
Corvids occupy environmental niches all over the world except in the polar regions and the tip of South America and tend to thrive in proximity to humans. They are omnivorous and will eat anything we will, which undoubtedly contributes to their extent and success.
The relationship between humans and corvids has varied over time, from mystical reverence to malign mistrust and aggression. However, like the old me, many people probably just ignore them or see them as a noisy nuisance. Hopefully the picture painted above will encourage a deeper appreciation of these remarkable creatures.
Paul O’Donoghue is a clinical psychologist and founder member of the Irish Skeptics Society. contact@ irishskeptics.org