The Red-winged Blackbird is by far one of the most well-known of North American birds. To many in the north and east, it is a classic harbinger of spring. When the Red-winged Blackbirds arrive at the local marsh, you know that the snow is about to disappear. Apart from its familiarity to birdwatchers, it is also a well studied bird in terms of its behavior, nesting and ecology. Red-winged Blackbirds are often polygynous, each male having more than one mate. This species was instrumental in the development of the “Polygyny Threshold Model” which seeks to explain when a female should choose to become involved in a polygynous mating relationship with a male. Red-winged Blackbirds have also been studied to understand the role of plumage in mate acquisition, through experiments where the bright red shoulders of males were painted black to see if this affected their ability to attract mates. More than any other single New World species, the Red-winged Blackbird has been an outstandingly important species in the science of Behavioral Ecology. Much remains to be understood about this bird, least of which is its taxonomy with rather different appearing populations in California and central Mexico that may be incipient species.