The reason why crows are considered to be one of the most intelligent birds is because they exhibit many advanced cognitive abilities, such as tool use, social communication, memory, and learning, among others.

Crows are considered to be one of the most intelligent birds in the world, mainly for the following reasons:

1. Problem-solving skills: Several scientific studies and observations have shown that crows have excellent problem-solving skills. For example, they are able to use tools to get food, such as fishing for insects in tree holes with twigs or smashing nuts with stones to extract kernels. This use of the tool shows the crow’s intelligence and ability to innovate.
2. Memory and learning ability: Crows have excellent memory, they are able to remember faces, places, and behavior patterns, and respond adaptively accordingly. Experiments have shown that crows can remember where their food is hidden for years, and can learn to copy other crow-making tools.
3. Social intelligence: Crows belong to the crow family of birds, which have complex social structures and communication systems. They are able to communicate effectively with other crows through chirping and body language, and can understand and remember hierarchical relationships within a group, and can even disseminate information and skills to other members of their kind.
4. Understanding causality: Research has revealed that crows are able to understand causal relationships between things, such as in laboratory conditions, by observing and learning to understand how complex mechanical devices work, and successfully manipulate them for rewards.
5. Affective expression and empathy: There is evidence that crows are able to express empathy and show caring behavior towards their injured or deceased peers, reflecting their cognitive complexity at an emotional and moral level.

Combining these characteristics, scientists and researchers generally agree that crows have a fairly high level of cognitive ability and intelligence, which makes them stand out among the bird kingdom and are known as one of the most intelligent bird species.