The male Red-winged blackbirds hang out during the fall and winter in large same-sex flocks as do the females when they aren’t mating and raising young. Then, during the breeding season, the males set on cattails calling and flying around, each in a small area with females in nests within the cattails nearby.
These are much studied birds, especially their social behavior. Much of the literature states as fact that the males are defending their territories against other males. The thing is, a huge percentage of the eggs in each nest are fertile from more than one male.
Since the blackbird males flock must be a close tribes during the non-breeding season, they must develop relations with each other bird in the flock. Perhaps they are sort of friends rather than how we often define animals as always in competition. Maybe it is more of a sharing system than we are able to realize, coming from our society’s identification with competition, male dominance, and monogamy as the dominant relationship patterns.