While some argue that the first robin is the true harbinger of spring, robins can often be found here and there during the winter. Instead, an irrefutable sight and sound of spring is a grove full of thousands of red-winged blackbirds, chattering noisily on a gorgeous spring day. These blackbirds are heading to their breeding grounds. Some will stay in Minnesota to nest while others push further north.
Red-winged blackbirds are particularly gregarious during migration; sometimes long narrow flocks of blackbirds will take five minutes or more to pass overhead, with the flock stretching for more than a mile and containing many, many thousands of birds.
Once they settle on a breeding site, blackbirds which were earlier happy to spend days with thousands of their own kind suddenly become deeply territorial. The males, with their widely recognized jet-black appearance and red shoulder markings, typically migrate a few weeks before the females. The later arriving females are often not identified as blackbirds by casual observers. Female red-winged blackbirds are a bit smaller than the males, and have a camouflaged, streaky brown plumage with no red markings.
The males select a breeding territory in a promising portion of a marsh, perch on tall cattail stems, and sing their happy spring song. It often takes many days for the birds to sort out their territories, with rival males taking as much marsh as they can defend from other males.
Watch a marsh on a spring morning when the blackbirds are freshly arrived. You will often see a male fly to a certain cattail stem and sing. Another male will instantly come, display his red epaulets, and sing from just a few feet away, defending his side of some invisible line they have created with passion and vigor. When the females arrive, they select not so much the male bird as the quality portion of marsh they believe will best serve their need for food and a secure nest site.
Frequently, two or three female blackbirds will end up in the territory of a single male bird which has been able to claim choice real estate. Male blackbirds will mate with all females which settle in their territories. The nests are typically woven onto upright marsh vegetation, with dense cattails being particularly favored.
About the time the male redwing blackbirds are getting their territories sorted out, the later arriving yellow-headed blackbirds arrive on the breeding grounds. They tend to dominate the red-winged blackbirds and often cause additional chaos as they force some red-winged blackbirds from choice spots in the marsh interior, setting off a chain reaction as the red-wings try to retain the most favorable territory possible given the new presence of the dominant yellow-headed blackbird. While the two species sometimes squabble over territories, they do not interbreed.
There are several other blackbird species in North America, including Brewer's blackbird, rusty blackbird, and tri-colored blackbird, but only red-winged and yellow-headed blackbirds are common nesters in western Minnesota.
Blackbirds, particularly red-winged blackbirds, occasionally cause some agricultural damage in the fall, especially in sunflower fields or rice fields. Huge flocks sometimes develop a pattern of roosting in a certain marsh and going by the thousands to a nearby field to feed. These problems are highly localized and, for the most part, giant flocks of blackbirds should cause a feeling of celebration and awe rather than annoyance. The giant springtime flocks of blackbirds are one of the great sights of the spring migration and a guarantee that spring has finally arrived.
Featured WPA: Loen Waterfowl Production Area, Swift County
The vast cattail marshes of Loen Waterfowl Production in Swift County are classic breeding sites for red-winged blackbirds. Loen is an 879-acre unit six miles northeast of Benson and three miles southwest of Swift Falls. The adjacent Svor and Tolifson WPAs abut Loen WPA and create a 1682-acre high quality block of public land. Loen and Svor WPAs both contain large marshes with somewhat more emergent vegetation than is ideal for waterfowl, but there are still open water pockets here and there throughout the system. The wetland edges and grassy upland sites on Loen WPA are being encroached by trees and brush which did not historically exists on these sites. Eventually, the Fish and Wildlife Service plans to remove some of this woody material to return the site to more open grassland habitat. Habitat blocks of this size are rare in the agricultural regions of Minnesota. Loen WPA is a fine place to do some spring bird watching and rejoice in the warmer weather.
For a map of Loen WPA or any other WPA in the district, go to http://midwest.fws.gov/ Morris.