Final answer:
The article 'the' is used before the phrase 'The crows are very cunning' to refer to the entire species collectively. This is a common grammatical structure in English when speaking about the general traits of a known group or species.
Step-by-step explanation:
The article used before the phrase 'crows are very cunning' should be 'the', as in 'The crows are very cunning.' This is because the phrase seems to be talking about crows in general, as a known group with a characteristic that is being attributed to them collectively. In English, when referring to a species or a group as a whole, we often use the definite article 'the'. This usage is demonstrated within various textual examples that describe the behavior of crows and other animals, indicating that these creatures are known for their intelligence and resourcefulness, such as in tool-making and interacting with humans. The crows' capacity for cunning behavior is further highlighted in narratives where they play significant roles or are remarked upon for their clever nature.