Answer:
The mating system Red-winged blackbirds have is Territorial Polygyny
Step-by-step explanation:
Males Red-winged blackbirds arrive before females, select nesting places and defend the territory where 5 to 15 females can establish nesting areas.
Males attract females for nesting by vocalizations and postures, and also having large territories with enough resources for living.
Females accepts the male and his territory and then starts building the nest.
On this type of polygyny, the association between the male and several females occurs on the male`s territory.