Territoriality is a widespread phenomenon in the animal kingdom. For many species, holding and defending a territory is necessary for reproductive success.
What has been perplexing to scientists, however, is the general rule that defenders almost always defeat challengers without actually engaging in a real fight. The act of confronting and threatening challengers seems to be enough to turn them away. Understanding how animals establish and maintain possession of their territories has been an important goal of scientists for many years.
Pioneering field studies of the male red-winged blackbird conducted by UW zoology professor Gordon Orians and post-doctoral researcher Les Beletsky have helped to explain the phenomenon of territorial dominance in animals. Orians has surveyed territorial movements of these songbirds over a 14-year period and identified the factors that affect which birds acquire territories. He has tested theories proposed to explain territoriality by removing dominant individuals from their territories for a time and then studying what happens when these "owners" are returned and must confront their "replacements." And he has elucidated the relationship between levels of hormones such as testosterone in male birds to their territorial dominance and reproductive success.
These experiments were conducted within marshes in and near the Columbia National Wildlife Refuge in south-central Washington State. Each year, from about late February through June, the researchers would tromp through some eight different marshes located on five lakes along a three-kilometer stretch of land. Within those marshes, they monitored all red-winged blackbird territories, searching them for nests and identifying all breeding males and most females.
Most people would probably just assume that the stronger, larger birds that are the best fighters would be most successful at acquiring territories. But Orians and colleagues found no evidence to support that theory. Rather, it seems the better competitors are the males that are more familiar with an area. Birds having greater familiarity with food sources, shelter, and predators seem to the be ones that are better able to establish and hold on to territories. For red-winged blackbirds, it seems, knowledge is the key to success.