Corvidae

Corvidae is a family of intelligent birds that includes crows, ravens, rooks, magpies, jackdaws, jays, treepies, choughs, and nutcrackers. There are currently 135 known species of corvids, with the genus Corvus alone containing 47 species. The raven is the largest type of passerine bird.

Corvids are known for their remarkable intelligence. They have shown self-awareness in mirror tests, like the Eurasian magpie, and can make tools, a skill once thought to belong only to humans and a few mammals. Their brain-to-body mass ratio is similar to that of great apes and cetaceans, and only slightly lower than humans.

These birds are medium to large in size, with strong feet and bills. They live worldwide except for the southern tip of South America and the polar ice caps. Most corvid species are found in tropical South and Central America and southern Asia, with fewer in Africa and Australasia. Some raven species on oceanic islands are highly threatened with extinction.

Systematics, taxonomy, and evolution

The name Corvidae was introduced in 1820 by an English zoologist. Corvids, which include crows, ravens, magpies, and jays, originated from ancestors in Australasia and spread around the world.

Scientists have studied their family tree using DNA, showing that jays and magpies split into different groups. Some birds once thought to be corvids, like the crested jayshrike, are now known to belong to different families. Fossil records of corvids go back about 17 million years, found in Europe and other places.

Morphology

Skeleton of (Corvus brachyrhynchos) at the Museum of Osteology

Corvids are large birds with strong legs and bodies. Most have special feathers covering their nostrils, except for the pinyon jay. Their feathers are often black or blue, but some tropical kinds are very colorful. Both males and females usually look similar.

These birds have strong beaks and big wings. The dwarf jay is the smallest, weighing about 41 grams. The common raven and the thick-billed raven are among the largest, often weighing more than 1,400 grams. You can tell them apart by their size, shape, and where they live.

Ecology

Corvids, such as crows and magpies, live in most parts of the world and usually stay in one place. However, when food is scarce, they may travel to find more. Crows are successful partly because they can share breeding areas more than birds like ravens, allowing more crows to live in the same spot.

While some worried that crows and magpies might harm smaller birds by taking their eggs, studies show this isn't a big problem. For example, American crows didn’t cause declines in marbled murrelets, and Eurasian magpies didn’t affect many songbird populations. Other factors, like habitat destruction, play a bigger role.

Behaviour

Some corvids, like jackdaws, live in organized groups with clear social roles. They help each other, such as sharing food and caring for young birds together. Young corvids enjoy playing complex games, like pretending to be “king of the mountain” or balancing sticks, which helps them learn important survival skills.

These birds also choose mates through playful contests and tests. Some corvids, like blue jays, can be aggressive when protecting their nests, sometimes chasing away animals that get too close.

Food and feeding

Corvids eat a wide variety of foods, including insects, small animals, fruits, and seeds. Some, like crows, have learned to live near humans and eat things like bread, spaghetti, and dog food. They are also skilled at finding and eating pests that harm crops, such as cutworms and grasshoppers.

Reproduction

Corvids often stick together in strong pair bonds and work as a team to build large nests. They usually lay between 3 and 10 eggs, and both parents help care for the chicks. Some corvids, like rooks and jackdaws, even live and nest in large groups.

Intelligence

A Canada jay pair feeding their chicks.

Corvids are known for their intelligence, with brains that are large compared to their body size. They can solve difficult problems, use tools, and remember where they hide food for many months. For example, New Caledonian crows make hooks from twigs to catch insects. Their smart behaviors help them survive in tough environments and live in complex social groups.

Disease

Corvids, such as crows and ravens, can carry the West Nile virus. They get this virus from mosquitoes, especially those of the Culex species. When these birds die from the virus, it can be one of the first signs that the West Nile virus has arrived in a new area. This was the case in 1999 when crows began dying in New York.

Relationship with humans

The Hawaiian crow is extinct in the wild as a result of habitat loss and other factors.

Some corvids, like ravens, have been kept as pets, though they are not as easy to care for as parrots and do not do well in cages. In the United States, it is illegal to own any migratory bird, including corvids, without a special permit under the Migratory Bird Act.

Throughout history, humans have shared spaces with corvids such as crows and ravens. These birds appear in many stories and traditions around the world. For example, some Native Americans believed ravens helped create the earth, while Celtic peoples linked them to war and the gods. In Germanic peoples myths, Odin had two ravens who brought him news from everywhere. Corvids are also popular characters in books and poems, showing their important place in human culture.

Species

Rufous treepie, Dendrocitta vagabunda

The Corvidae family includes crows, ravens, magpies, jays, and nutcrackers, among other birds. There are 135 species in this family. The genus Corvus alone has 47 species, making up over a third of all corvids.