Blackbirds tend to be solitary birds. Small feeding and roosting aggregation sometimes form at good sites, but there is no proper social interaction.
Male blackbirds establish a territory during their first year, which they will hold throughout their lives. The territory is essential for pair formation and nesting, although only a part of the food is obtained from within it.
Territory size varies depending on the habitat, and can be as small as 0.2 ha. Territory boundaries break down when the last broods have fledged and adults moult. During this period, territorial drive is low, and many birds will feed outside their territories at abundant food sources.
Territories are re-established in the late autumn, and from spring until July they are defended against all other blackbirds.