Crows: The IQ of Birds

Engels’s famous saying was once quoted in middle school textbooks: “The ability to make and use tools is the essential difference between humans and animals.” It is true that most animals are not very good at using, let alone making, tools. In people's minds, only some more advanced primates, such as gorillas, can use branches to break them to the extent they need and then dip them into termites to eat. In other animals, "advanced skills" in tool use are not developed.

However, ornithologists don’t see it that way, at least crows are a special case. In 2005, at a scientific conference in Washington, Louis Lefebvre of McGill University in Canada released a research report on bird intelligence. They summarized 2,000 bird innovations in nature. Feeding observation reports and bird research papers published in various countries around the world in the past 75 years have listed a ranking of bird IQ, among which crows ranked first. Scientists have long noticed that some species of crows are able to use and even make tools to help themselves find food. Compared with most other birds that can only rely on their own beaks and claws to get food, crows are really much smarter in this skill, and they deserve to be ranked first in IQ! So, let’s get to know this group of clever crows.

The New Caledonian crow: an outstanding representative of smart crows

In "Aesop's Fables" there is a very famous story "The Crow Drinks Water". The content of this fable has now been Scientists confirm. In a study published in the Public Library of Science - General, zoologist Sarah A. Jelbert from New Zealand and others studied the New Caledon crow ( The foraging behavior of New Caledonian Crows was studied.

They placed the food in a glass tube filled with water. Because it was some distance from the mouth of the tube, the New Caledonian crows could not directly come into contact with the food. However, they soon discovered that by dropping a small stone next to the tube into the water, the food would rise until it could be pecked at. Not only that, they were able to differentiate between bottles containing sand and water, because throwing stones into a glass tube containing sand did not cause the food to rise (Figure 1A); they were able to differentiate between light and heavy objects. , because light blocks will only float when thrown into water (Figure 1B); they will use solid blocks instead of hollow blocks because the latter will not cause the liquid level to rise (Figure 1C); they will also between thin and thick bottles (Figure 1D), and between high and low water bottles (Figure 1E); even more surprisingly, in the U-shaped tube experiment, the glass tube on the right and the middle The food tube on the left was connected, but not on the left. After several attempts, the New Caledonian crow correctly selected the glass tube connected to the food (Figure 1F). Picture (1), testing the ability of crows to obtain food from water in different modes.

New Caledonian crows are tropical crows that live on the island of New Caledonia in the South Pacific. They are smart, curious, and like to play. What is even more peculiar is that they are very good at using tools and can even use the tools around them. materials to make your own tools. Christian Rutz, an ornithologist at the University of St. Andrews in the United Kingdom who has studied the behavior of New Caledonian crows for more than a decade, said that New Caledonian crows are one of the very few corvids known to use tools. Family, Coridae, with 23 genera and 117 species, generally including crows, ravens, rooks, crows, magpies, tree magpies, gray birds and other birds). For example, in the picture below, they will bend some branches to "grab" food in the gaps. Randomly captured wild crows bend tree branches into "hooks" to "pick out" food in tree holes.

A new member of the “Tool Users”: Hawaiian crows

Is the New Caledonian crow the only corvid that is born with the ability to use tools? This question has troubled ornithologist Lutz, who has been studying New Caledonia crows for more than ten years. Moreover, the evolutionary origins of this tool-using behavior have been elusive because there are no other species of the same genus for comparison. Then keepers at the San Diego Zoo Global noticed that another tropical corvid, the Hawaiian crow (Corvus hawaiiensis, commonly known as ‘alalā), was also very good at using tools. They collaborated with Lutz and others to conduct research on the behavior of Hawaiian crows. Recently, the research results were published as a cover article in the top international journal "Nature". Left picture: A Hawaiian crow is "seriously" holding a twig in its beak to feed from a hole.

Right: Cover of the journal "Nature" - "Hidden" Genius.

Hawaiian crows mainly live in forests, and their main food is lizards, seeds, insects, etc. However, at the beginning of the 21st century, Hawaiian crows have become extinct in the wild (possibly due to habitat changes, hunting by people, the spread of plague, etc.), and the surviving ones are all in captivity. Therefore, the researchers conducted experiments on 104 of the 109 existing Hawaiian crows (the remaining 5 did not participate due to health reasons).

First, they designed two different experimental facilities. One was a tree trunk with several horizontal and vertical holes and grooves drilled; the other was a tree trunk with several small holes and grooves. A small fluted wooden platform. They then placed food in the holes and slots to observe the crows' tool use. "We've known for a long time that Hawaiian crows are highly intelligent, but until this experiment we didn't realize just how good they are at using tools," said researcher Bryce Masuda. For example, almost all crows can use tools, and 78% of crows will spontaneously use sticks to test food that is not directly accessible. Only one successful attempt took more than a minute. The crows can find sticks of the right length and replace those that don't fit, and are frequently seen modifying tools. Of the crows tested alone, 67% were able to peck an overly long stick shorter. 14% of crows make homemade tools from surrounding branches and other materials. Tool use was not related to gender, but was related to age: 93% of adult crows used tools, compared with 47% of juvenile crows. A device used to test the ability of crows to use tools to obtain food.

So, is this complex pattern of tool use innate to these crows? Or is it through acquired learning (learning from other crows or learning from humans)?

Scientists think it is the former. Because, first, almost all crows have the ability to use tools; second, they raised seven young crows independently so that they could neither learn this skill from other adult crows nor from humans. Untrained Hawaiian crows still displayed rich tool-using behaviors. These two facts, along with other evidence, suggest that tool use is an instinctive behavior among Hawaiian crows. Their foraging behavior requires them to be constantly looking for things, and this tendency to use tools to assist foraging may be caused by this and has been engraved in their genes. Of course, individual learning and socialization also have an important impact on their behavior. In addition, because Hawaiian crows are extinct in the wild, we cannot observe their life in the wild. Current observations tend to believe that they are also capable of using tools in the wild. In addition, because the Hawaiian crow and the New Caledonian crow are relatively distant, their living environment is similar: they both live on remote tropical islands. The authors believe that it is this similar ecological condition - such as less foraging competition from local prey and low risk of predation - that drove their convergent evolution, learning to use tools for foraging, and evolving it into an instinctive behavior.

There are currently just over 100 captive Hawaiian crows left in the world, but later this year some of them will be released into the wild, allowing scientists to observe their tool-using behavior in the wild.

Hawaiian crows will also hopefully recover in the wild, which may be difficult, but we look forward to that day!