While there is no species of bird that dominates over all the other species, there are dominant birds within each species. Consider the military -- each higher rank has fought for and proved his worthiness of that rank, and it is much the same for birds. Dominance plays a large role in bird communities and helps establish a pecking order so that each bird knows its place and order can be maintained in the flock.
Why Dominance Matters
Natural selection requires communities comprised of both stronger and weaker individuals so that eventually only the ablest and smartest will survive and evolve. In birds, dominant flock members get to eat first and therefore have better pickings, thus leading to better health and body condition than their subordinates; this helps them avoid being prey. Dominant birds are less prone to getting into fights and obtaining injuries within their flock -- lower ranking members recognize that they are stronger and will not attack them. Dominant male birds get more and better mates. Dominance also helps to establish who reigns over a specific territory.
How Dominance Is Established
When a bird has been positioned as a lower ranking flock member, it means they get what's left over at feeding time, have a higher risk of being fought and injured by other flock members, and often experiences decreased health. To overcome this, birds fight each other to gain dominance. Once dominance has been established, the flock will remember and keep their place. Gender and age are also large factors that play into the pecking order. In a study by the Ohio State University, one species' order of dominance is as follows: adult males, juvenile males, adult females, juvenile females.
Though theories differ on why male birds fight each other, the fact remains that they do fight in competition to gain dominance over territory, females or both simultaneously. Scientists hypothesize that the stronger male will appear more appealing to the females and in turn they will want to mate with him. Territorial fights not only serve to drive the weaker male out of the stronger bird's territory but also leaves all the females in that area to the dominant male. Fighting includes pecking and biting, attacking with claws, and beating with wings.
Since female birds are the breeders, they must establish dominance over the territory of where they will have their nest; this keeps away other females who may want the area. Many female birds also become dominant over the male once a pair has created a bond -- after all, it is the female's choice of who she will mate with. Once she has chosen a male, it becomes his job to secure a site and build the nest all under her watchful eye. Some female birds even leave the males to incubate the eggs once they are laid.
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