In the week before the Summer Solstice, a bit earlier than last year, an unaccustomed quiet has settled over the northwest quadrant of the park. The Red-winged Blackbirds have finished their breeding and all except a few females, such as this one above, have flown off. Where they go I do not know. The fennel forest which has sheltered many of their nests has dropped nearly all of last year’s seeds, and the green new shoots of this season are breaking into flower. If the past is a guide, an early crew of males will return in January to scout the site; they will leave and be replaced by others, all checking to see whether the females have arrived yet. When the females do arrive, bird bedlam breaks loose.
An interesting study done in the early 1970s explored the role of the males’ red shoulder patches (epaulets). The experimenters captured males and covered their epaulets with a permanent black dye, They found that the majority of the blackout males lost their territories to unmodified rival males. But the females didn’t care. They mated as well with the blackout males as with the red ones. Red-winged blackbirds are polyamorous, with both males and females having a number of sexual partners, and most egg clutches having multiple paternities. With the blackbirds, the evolutionary purpose of the red epaulets is not to woo the females but to impress other males. Source.