Researchers have found that crows can hold grudges against humans for up to 17 years after they are angered or threatened. A study by Professor John Marzluff at the University of Washington, which began in 2006, involved wearing a scary mask to attract crows and observe their behavior.
The study showed that crows can recognize faces and learn to associate threatening humans with negative experiences. After peaking in 2013, the number of aggressive “scolding” calls from the crows decreased significantly over time, eventually falling to zero after 17 years.
In another experiment, volunteers wore masks deemed “dangerous” or “neutral” by the crows and reported being subjected to aggressive behavior. The study highlights the remarkable intelligence and memory of crows, which are considered one of the most intelligent bird species.
This finding has been corroborated by reports from residents in London’s Dulwich area, who have experienced a series of dive-bombing attacks from crows this year. While the exact cause of the aggressive behavior is not clear, it appears that some crows may hold grudges against specific individuals or groups for extended periods.
Source: https://www.dailymail.co.uk/sciencetech/article-14031921/crows-hold-grudge-birds-grumpy-17-years-study-washington.html