Crows hold grudges for 17 years.
Crows hold grudges for a long time
The birds are renowned for their intelligence and a new study has revealed that they have long-term recollections of those who anger or threaten them.
The research started back in 2006 when Professor John Marzluff, an environmental scientist at the University of Washington, put on a scary mask and captured seven crows in a net.
They were all released unharmed but he put identification rings on their legs.
Professor Marzluff and his assistants would occasionally wear the masks in the following years as they walked around campus feeding the crows with the boffin recalling how he received aggressive 'scolding' caws from 47 out of 53 birds.
The expert suggested that crows are "very, very keen at noting our actions".
Professor Marzluff said: "That they pay so much attention to people has been one of the most surprising things to me in my work with them."