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.
Other amazing phenomena to observe are the massive and hypnotic “murmurations” of such birds as red-winged blackbirds and European starlings. While here in Minnesota it is usually only blackbirds that gather in such huge and endless flocks, people in Europe witness the same behavior of their native starling.
Murmurations are fascinating to watch. The enormous undulating flocks move through the sky as if it were an organism by itself. In a sense, it is. Each individual bird is miraculously able to keep a “personal space,” if you will, between themselves without crashing into one another.
According to a research study that analyzed murmurations, it is believed that each member of a murmuration has the ability to watch “seven others irrespective of distance.” Indeed, results of the study pointed out that as each bird keeps tabs on other nearby birds while maintaining safe distances from their neighbors, the murmuration functions as one giant pulsating flock. Even so, why or how birds evolved this type of flocking behavior will probably never be fully understood.
But this we do know: Fish and wildlife that band together, herd together, school together, and flock together provide many advantages to not only the individual, but to the population as a whole. The more individuals there are, the more eyes to notice potential threats and food sources. Survivorship – living another day to breed and raise young and carry on one’s genes – is the ultimate goal.
With birds, flocking enables them to exploit located forage and to confuse predators. And, as we’ve also come to know, a good reason to appreciate the old adage that; “Birds of a feather flock together” as we get out and enjoy the great outdoors.
BLANE KLEMEK is a Minnesota DNR wildlife manager. He can be reached at firstname.lastname@example.org.