Group of crows, known as "roosts"

Today a large group of crows were covering about five trees close to my house.
One of the great animal phenomena of the world is the congregation of large numbers of birds into a single group to sleep together. Such communal sleeping groups are known as "roosts. For crows, roosts are primarily a fall and winter thing. Numbers peak in winter and then decrease near the beginning of the breeding season (usually in March). It appears that all crows will join winter roosts, even territorial breeding crows. Most breeding crows sleep on their territories during the breeding season, but join the roosts afterward.