Historically the Red-shouldered Blackbird was considered an unusual subspecies of the widespread Red-winged Blackbird (Agelaius phoeniceus). Red-shouldered Blackbirds are endemic to the marshes of Cuba. The males look very much like Red-winged Blackbirds, but the females are not streaked but are solidly black, similar to the male but lacking the red and yellow epaulet. In Red-shouldered Blackbrids the male and female are also of a similar size, the two sing a very similar song and often duet with each other. When foraging for the young, the males and females provision at similar rates and the overall breeding system is monogamous, quite in contrast to the polygynous breeding system of the Red-winged Blackbird. In addition, juvenile plumages are blackish and like the adults. It was the behavioral differences of the Red-shouldered Blackbird that first alerted biologist to the potential that this was a different species from the Red-winged Blackbird. But more recently this has been confirmed by molecular techniques, and it also appears clear that the Red-shouldered and Red-winged are each other’s closest relative, with the Tricolored Blackbird (Agelaius tricolor) an earlier branch in this group of related species. Otherwise little is known about these blackbirds. They nest in marshes, and stay in marshes throughout the year. They also feed within their territories, and do not exit the territory to feed elsewhere from where they are nesting as is typical in North American marsh nesting blackbirds.