Flocking behavior offers birds advantages
One of the most interesting aspects of birds is their flocking behavior.
Of course, it isn't just birds that flock; other animals also gather together in large numbers. Over the African Serengeti, for example, great herds of wildebeest stretching endlessly across the landscape hearken to a bygone era when 60 million American bison once roamed the New World's Great Plains.
Yet it is with birds that we most frequently associate migration of the masses. The pulsating, undulating flocks of red-winged blackbirds that appear as noisy black ribbons extending from horizon to horizon during their annual autumn migrations are as spectacular as they are mesmerizing. So, too, are the biannual migrations of waterfowl that occur throughout the Mississippi Flyway and other thoroughfares.
But why exactly do birds flock in the first place? Why do some species of birds gather in such incredible numbers? Obviously, there must be some kind of benefit to the bird as a species for such a behavior to have evolved and persist. And that, as it turns out, is indeed the case.
There are two fundamental reasons why birds flock: flocking reduces the risk of being preyed upon, as well as permitting birds to forage together in cooperative ways. Regarding the former, "safety in numbers" is what it's all about.
Think about a family group, or flock, of Canada geese foraging in a field. While most of the geese will be engaged in feeding or resting, you will probably observe that some geese are not feeding. These non-feeding geese are usually adult birds serving as sentinels. They stand erect with their black necks stretched fully vertical and their watchful eyes searching for danger. If you approach the birds, the "lookouts" will sound an alarm that instantly alerts the others.
This type of behavior provides foraging and resting birds, of all species, with an important sense of security. In another example, individual group members of foraging ostriches randomly pause to search for lions or other would-be predators. And like grazing Canada geese, at least one ostrich in the flock serves as a guard. If danger is detected, ostriches can communicate in ways that enable them to escape together.
Ducks also have this ability, in addition to incorporating body language that helps facilitate synchronized takeoffs. I've witnessed this behavior many times in flocks of ducks such as mallards. It's amazing to observe -- hundreds of birds feeding in a bed of wild rice suddenly exploding into the air at once. It's made possible when one or more of the birds detects you. As these individual birds begin to ready themselves for flight, others notice and follow suit. Soon the entire flock is poised. If one bird flushes, the entire flock flushes in one fell swoop.
Flocking also makes it difficult, not to mention dangerous, for birds of prey such as falcons to successfully capture and kill an individual bird within a flock. A raptor preying on flocked birds risks serious injury or death if it attempts to enter the middle of a large, tightly packed flying flock of starlings or other similarly behaving birds. A high-speed, mid-air collision could easily occur if the raptor is unable to react in time if one or more of the panicked birds enter into its flight path.
Flocks create "predator confusion," as it is called, for predators. And this phenomenon can also happen with human predators. A classic example occurs in the duck blind. Waterfowl hunters, for instance, are taught from an early age that in order to shoot and kill an individual duck or goose amongst a flock, one needs to learn how to concentrate on a single bird while simultaneously ignoring the others. It is no different for an avian hunter, like a merlin, as it attempts to zero in on a lone bird flying at the outskirts of a flock or lagging behind.
Gathering in groups also benefits birds through cooperative feeding behaviors. A good example of this occurs in the feeding style of American white pelicans. These birds commonly swim together in order to drive small fishes into shallow water where capturing them is easy.
I remember once watching a large group of pelicans in the shallows of a North Dakota wetland. The birds had completely encircled and trapped tens of dozens of larval tiger salamanders. As individual pelicans gorged themselves on their catch, ring-billed gulls, evidently attracted to the fracas, joined the feeding frenzy and began stealing salamanders from both the water and pelicans' beaks. In this particular case, two different species of birds were the benefactors -- each taking cues from one another.
Other birds, like black-capped chickadees, frequently forage together in loose flocks. The birds are constantly communicating to one another as they flit from branch to branch searching for insects and seeds. Individual birds that happen to locate abundant food sources are quickly noticed by other nearby birds and, thus, serve as a boon to other members of the flock.
Banding together is definitely an advantage to many species of wildlife, especially to birds. The more there are, the more eyes to notice potential threats and food sources. As well, flocking enables birds to exploit located food and confuse predators. And, as we've come to know and appreciate, there are many reasons why "birds of a feather flock together" as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org