You have likely noticed that the red-winged blackbirds are busy in area wetlands. This blackbird with the red epaulets is one of the most recognizable birds here in North Dakota and one of the most abundant birds in North America.
This is a busy time for red-winged blackbirds. Although we see them in large flocks during the fall, now during the breeding season they are not very sociable, particularly the males. As you look out on area marshes and see the males perched atop a cattail or bulrush, those males are staking out and defending their turf.
The breeding season for red-winged blackbirds runs from March through August. Breeding males will generally occupy a territory of around 2,000 square yards. If that territory were a square, it would be around 40 feet on a side.
Males are fierce defenders of their territory during the breeding season. As you would expect, they will chase off other males. But other interlopers are also not welcome. They commonly chase off a variety of predators and other intruders much larger than themselves. It has been estimated that a male will spend over one-fourth of the daylight hours defending their territory.
All that effort, however, does not ensure his paternity of young produced within his territory. Red-winged blackbirds are polygynous, with each breeding male having several nesting females within his territory. As many as 15 nesting females have been documented in a male’s territory, but the average is around five. But trysts are common, among both males and females. Somewhere between one-fourth and one-half of the young in any particular territory may be the offspring of these trysts.
Trysts aside, the breeding females will generally construct their nest among the tall emergent vegetation such as cattails and bulrushes. She may produce 1-2 clutches per year, with each clutch consisting of 3-4 blue-green or gray eggs with black or brown markings.
So the next time you see the red-winged blackbirds on area marshes, you might want to take a few minutes to observe their behavior. Expect plenty of activity. Their mating system appears to be working quite well, and before we know it, they will be flocking up, along with the youngsters, and heading for warmer climates.
Chuck Lura
Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Dakota College at Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.
