Crows are one of the most intelligent bird species according to bird watching guides. Researchers are exploring algorithms to quantify the experience levels of citizen scientists who contribute data. Groups of crows harassing ravens may be more noticeable than single crows, but the current data set cannot evaluate this potential bias. Crows roost in treetops at the end of the day, traveling from up to 20 miles away to congregate. They eat a variety of foods including mammals, insects, and small birds.