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The crow family is made up of over 100 different species of crows, jackdaws, ravens, rooks, magpies and jays. They are widely distributed globally, highly adaptable contributing to their success and they demonstrate incredible emotional and cognitive abilities.
Crows are social animals and develop strong bonds with birds in their family group. In some species, mated pairs share territories with their grown children. The older offspring in turn help their parents with raising each season’s new brood of young birds. Living in the family group also makes them happier and being happy and less stressed helps to keep them fit and healthy.
Brown Jays make nesting a family affair. The entire flock which can be over 12 individuals takes care of a single nest, which holds four eggs laid by one female in the flock. Each bird brings food to the young in the nest. When the young leave the nest they are vulnerable and naive, nest helpers then teach the young to find food and recognise danger. Complex skills necessary for survival to adulthood. In turn the youngsters may inherit the nesting territory when they come of age.
Helpers in American crow families bring sticks and other nesting material to help the female build the nest. Throughout the incubation period, the female spends 90% of her time incubating. She is fed by her mate and the rest of the helpers a few times per hour.
Once the eggs hatch, parents and “helper crows” make more than 20 visits per hour to feed the nestlings and the young birds continue to be fed exclusively by older crows for at least two weeks after they leave the nest.
Many crow species live in family groups and many including Jackdaws stay with their partners for life, raising their chicks together and even flying side by side within their own flock and benefitting by needing to use less energy in flight.
Ravens are also known to develop alliances with other individuals through affiliative interactions such as grooming and playing and they will actively seek to maintain these alliances and prevent other individuals from breaking them up.
Azure winged magpies share their food. If one bird has access to a lot of food and another does not, the bird with the most will give some of their food to the other bird to ensure everyone in their family group can eat. The magpies are more inclined to share food with their peers. They differentiate, however, between whether others have food or do not have food, and subsequently provide food to those that have none.
Azure-winged magpies are cooperative breeders that raise their young together and cooperative breeders have a strong tendency to help each other. About 40% of the 116 species in the crow family (including jays, magpies and nutcrackers) are cooperative breeders.
Ravens are also known to cooperate with each other when more than one individual is needed to access a food reward, and this cooperation is the most effective between individuals that have developed a friendship.
Crows are able to visualise a problem, plan a course of action to overcome the problem and carry it out successfully, they can make their own tools, and both plan and carry out a task using many different tools to reach a food reward. Not only do they make and use a variety of tools they also understand the basic concept of cause and effect.
The most striking example of this has been observed in crows that have successfully mastered a complex puzzle consisting of 8 separate stages. Each stage posed its own problem, which when solved, provided a tool that could be used to solve the next stage. This act of using one tool on another is called metatool use, a significant indicator of intelligence. Every stage had to be solved in successive order for the entire puzzle to be completed. For a crow to solve the puzzle, it would need to employ both its metatool use skills and understanding of cause and effect. Impressively, crows are able to solve the puzzle with relative ease.
New Caledonian crows have demonstrated their ability to choose tools of the right length for the task in hand, can make tools of the right diameter for a problem, and will risk their tools, rather than their beaks when faced with hazardous objects such as a model snake (context-dependent tool use).
New Caledonian crows are also known to manufacture new tools by adding useful new features to their insect-snagging tools fashioned from leathery pieces of torn leaf. And these innovations are faithfully passed on between individuals and across generations. Crows snip into the leaf edges and then tear out neat strips of vegetation with which they can probe insect-harbouring crevices. These tools have been observed to come in three types: narrow strips, wide strips and multi-stepped strips—which are wide at one end and, via a manufacturing process that involves stepwise snips and tears, become narrow at the opposite end.
It is hypothesised that the crow has developed the capacity to evolve its tools, an important step in the direction of a complex material culture, like that exhibited by people.
Rooks have been shown to choose between functional and nonfunctional tools, to spontaneously use sticks as tools and to spontaneously modify sticks so they can be used as tools. Both species have also produced meta-tool behaviors where they use tools to gain access to other tools which can be used to get food.
One of the most impressive behaviors produced by both these species is the bending of man-made material into hooks. After using a wooden hook to pull a bucket by its handle from a tube, Betty, a New Caledonian crow, subsequently bent a straight piece of wire into a hook shape in order to do the same. Rooks, given similar experience using a wooden hook to pull a bucket from a tube, also then bent wire to make a functional hook.
Both rooks and New Caledonian crows have been able to solve the trap-tube problem, where an individual has to pull food from within a horizontal tube while avoiding a trap, and new caledonian crows have been able to transfer their skills from the trap-tube to the trap-table problem.
Rooks, crows, and Eurasian jays can, like children learn the functional properties of stones and stone-like tools when dropping these objects into a water filled tube to raise the water levels to retrieve a treat on the water’s surface
Urban-living carrion crows in Japan have learned to use road traffic for cracking tough nuts. The birds drop the nuts onto a busy road and then await a vehicle to drive over and so crush the nut, before returning to the crushed nut to eat. This is a somewhat risky strategy as it involves eating in amongst the traffic and therefore some individuals have since refined their strategy. They carry out this behaviour above road sections with traffic light crossings, to maximise the chances of a car crushing a nut on the crossing, they then wait for human pedestrians and when the traffic is stopped by the red light they head out into the road to retrieve their prize.
Crows, much like humans, are also known to store their tools when they don't need them. Crows hold tools in their bill when foraging, but need to put them down to eat their prey, and in many cases, they will carefully place tools under their feet, to use them again later.
Experiments with wild-caught birds have shown that crows look after their tools more carefully when foraging at height than on the ground, and crows have been observed storing their tools in tree holes or behind bark for future use.
The crows are extremely good at keeping track of their tools, remembering where they had put them, and reusing them again to extract more meals shortly after. This tool storage behaviour is very important, as it means crows don't have to repeatedly manufacture new tools and can spend more time on the critical business of finding food.
Jackdaws tell other birds in their family about potential dangers, for example if a person is not nice to one particular bird. This bird warns the others to stay away from this person when they see the person close to their nest site. They are known to recognise individual people, and respond differently to those they see as a threat.
Siberian jays live in family groups that can include not only the young of a breeding pair, but also young that were born in other groups. These young can stay with the family group for up to four years. Young birds that stay with their parents longer benefit from being with their parents. By learning the skills to both find food and to avoid predators. As a consequence, they are more likely to live longer and to start their own family.
New Caledonian crows learn key survival skills from their parents such as how to make tools for food retrieval. It takes about a year to learn this skill and these crows may stay with their parents for up to three years, allowing for a much longer "childhood" than most other crows. Parents and other adults are extremely tolerant of young crows. While adults are using a tool to get food, they feed the juveniles, let them watch closely, and even tolerate tool theft and physical contact by the youngsters. As a result of this tolerant learning environment, New Caledonian crows have the largest brain size for their body size of all corvids.
Crows gather in large groups and share information about the local environment when they find a dead member of their own species in a particular area, helping them to learn and avoid the same fate.
Magpies have also been seen burying their dead under twigs of grass in a similar way that we would bury our dead.
Crows have their own calls which are different to that of others living in their family, this means that birds in a group can recognise each other just by listening to their calls, and crows can even discriminate between human voices too.
If a raven is burying food so that he can eat it at another time but he is being watched by another bird, he may pretend to bury the food in one place but actually bury it elsewhere. This is to try to fool the watching bird and prevent them from finding his food.
Ravens have been seen sliding down steep, snow-covered roofs. When they reach the bottom, they walk or fly back to the top, and repeat the process over and over again. Ravens have also been observed tumbling down small mounds of snow, sometimes while holding sticks between their talons. There is no obvious utilitarian function for this sliding behaviour, but the individuals appear to enjoy this activity.
Following conflicts over resources or dominance between ravens, bystanders console and relieve the distress of victims with whom they have a relationship, and victims are likely to seek affiliations with bystanders, and such affiliations help to reduce the incidence of repeat attacks.
According to the International Union for Conservation of Nature (IUCN), most crows are not endangered. The Flores crow is one of the exceptions. It is listed as endangered because it has a very small population that is on the decline as deforestation threatens its home on the Indonesian islands of Flores and Rinca. The IUCN thinks that its population is around 600 to 1,700 mature individuals. The Hawaiian crow is extinct in the wild with captive breeding and reintroduction projects and habitat restoration underway.
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