Did You Know? The total brain-to-body mass ratio of corvids is equal to that of great apes (like chimpanzees, gorillas, and orangutans) and cetaceans (like whales and dolphins), and only slightly lower than in humans. Because of their remarkable cognitive abilities, they are often referred to as 'feathered apes'.

Classification

Corvidae Family

American Crow

➺ Corvids found in temperate zones usually have black or blue colored plumage, while those found in tropical zones are brightly colored. However, some corvids of the temperate zone are black and white (magpies) or may have a blue-purple tinge in the plumage. ➺ Three of their toes point forward and one points backwards. This is a typical feature of passerine birds. This arrangement of toes facilitates perching. ➺ They have robust legs and feet, and stout and strong bills. ➺ Some of them have short tails while some have long ones. Usually, the tails are rounded. The wings also tend to be rounded. ➺ These birds are omnivorous. They eat invertebrates like crabs and snails, insects, earthworms, eggs, chicks, small mammals, spiders, berries, fruits, seeds, grains, and even carrion. Larger birds can eat smaller birds. ➺ Corvids usually nest on trees. However, they can nest in shrubs, on cliffs (ravens and choughs), or even on the ground. You may find a nest hidden in the vegetation. Some species (like rooks) breed in colonies. ➺ The clutch usually contains one to four eggs. Only the mother incubates the eggs. The father and other helpers feed her. After several days, the young birds become capable of flying. ➺ A pair or a flock defends a territory. Corvids use several displays to communicate, to impress the partner, to threaten a trespasser, or to defend the territory. They have large wingspans. The courtship displays are pleasant to watch. ➺ Although corvids do not sound musical like other members of the order Passeriformes, the sounds they utter depict their personalities. Some of them can mimic human voices and whistles. Some can even copy the calls of other birds.

➺ The dwarf jay (Aphelocoma nana), at 41 g (1.4 oz) and 21.5 cm (8.5 inches) is the smallest corvid, while the common raven (Corvus corax) and the thick-billed raven (Corvus crassirostris), which weigh more than 1400 grams (3 lbs) and can be about 65 cm (26 inches) long, are the largest corvids. ➺ Studies show that during breeding seasons, crows extend their territories significantly. The breeding territory of crows can be quite larger than that of ravens. This invasion of breeding territories is responsible for the significant increase in the population of crows as compared to ravens. ➺ Studies also show that the crows have the most diverse diet of all. They eat anthropogenic (resulting from human activity) foods such as bread, spaghetti, fried potatoes, dog food, sandwiches, and livestock feed. This has resulted in the increased population of crows. ➺ Corvids are aggressive, quarrelsome, and opportunist by nature! They can steal eggs and chicks of other birds. ➺ Corvids who lack the specialized beak cannot tear flesh of animals. When the animals are torn open, (by other birds/animals, or as roadkill), these corvids eat the carrion. ➺ Most passerines molt twice, but corvids molt only once in a year. ➺ Corvids are monogamous, often for the life.

Scientists had previously thought that only the primates can make tools. However, they have found that birds can also craft tools in the wild. They make tools from twigs and leaves, and use them to reach the food. Scientists have proved that corvids can think like humans. Here are some examples that show extraordinary intelligence of corvids. ➺ The fan-tailed raven uses stones to break open eggs. ➺ Common ravens (Corvus corax) make their own toys. They break off twigs to play with. ➺ The 'New Caledonian Crow', (commonly known as 'qua-qua') finds/makes its own tools. With the help of the tools, it extracts larvae from dead wood. This crow is perhaps the most accomplished tool maker among animals. It uses tools such as a 'hooked-twig tool', a 'hook-shaped wide end', and a 'stepped-cut tool' made from barbed leaf edges of screw pines. This 'larva fishing' is quite similar to the 'termite fishing' practiced by chimpanzees. ➺ In some Japanese cities, crows drop hard-shelled nuts on pedestrian crossings, and when the traffic stops, they collect their cracked nuts safely! In America too, crows drop walnuts onto busy streets so that they are cracked by running cars. This proves that corvids have a tendency to find new solutions to problems. ➺ The American crow can modify a piece of wood and can make a useful tool from it. It chooses a branch, chops off the side branches, and sharpens the end to make a hook! The tool is often used as a probe. ➺ With a small twig, the Green Jay (Cyanocorax yncas) can extract insects from the bark crevice. ➺ Captive Blue jays (Cyanocitta cristata) have used strips of newspaper as tools to obtain food. ➺ Hooded crows (Corvus cornix) use bait to catch fish. ➺ Studies have shown that these birds can craft new tools out of unfamiliar materials. While carrying out complicated tasks, they can even use different tools in succession. This is really very surprising. Sequential tool use represents a higher cognitive function. For the first time, scientists could observe this type of ingenuity in non-trained animals. ➺ When the food was within reach and was placed next to a model snake, the New Caledonian crow used stick tools to make first contact with the food and checked the safety. Several studies show that corvids are the most innovative birds. ➺ According to the researchers, crows do not learn their skills from their peers. They develop their tool-using abilities by 'keeping it in the family.' ➺ The Eurasian magpie is the only bird that has passed the mirror test. These magpies were able to recognize the image in the mirror as their own. Whether recognition of one's mirror image means self-awareness is a topic of debate. ➺ According to the study reports, the European magpie's brain consists of 31 percent of its total body weight, while the brain of an African gray parrot (popular as a talented talking parrot) is 22.6 percent of its total body weight. ➺ Studies suggest that corvids and great apes can make geometrical measurements.