.When I lifted the shade of my office window on January 1st, I looked out at 19 blue jays in constant motion flying from one bird feeder to the next. Then something I could not hear or see set off an alarm and they were gone in a flash. A short time later, when the all clear was sounded, they came back like a squadron of fighter jets, zooming in and scattering the few chickadees that had filled in during their absence. They were behaving as a flock, as do many other bird species. In fact when I think of all the bird species, there are very few that don’t, at some time in the year, form a flock or aggregation. Why they do this is a matter of conjecture and research.
Most people see flocks of birds most easily in the autumn when many species are gathering together in preparation for the journey to warmer and more productive feeding grounds. Ducks and geese quickly come to mind, since they are large and often noisy in flight, but grackles and other blackbirds are also form large flocks, moving in a compact linear mass that undulates up and down and sometimes swirls and twists – this is called a murmuration.
The reasons that have been given for this behavior of joining with a large number of other birds – usually of the same species, but not always – are the following: finding food, vigilance and protection from predators, an aid in migration, finding a new territory or mate, and learning particular behaviors.
The most easy to understand are the first two. Oftentimes flocks are observed feeding – in trees or on the ground, depending on the species. Many eyes are better at scanning the ground below and eventually someone is going to spot something that looks like food. Then all the other birds can follow and partake.
The same effect of many eyes not only helps find food, but serves as an excellent scanning and alarm system for predators, both on the ground and in the air. Most birds are hyper-sensitive to any sort of disturbance and will take off quickly if one of their members does. Small flocks tend to scan more often and for longer periods than those in a large flock. And birds along the edge of any flock will, not surprisingly, scan more often then those in the center. There is strength (or semi-protection) in a large flock, unless you are on the outskirts. In some species, including my favorite – the corvids (crows/ravens/jays) – one individual will act as the sentry and take a perch at a higher elevation in order to alert the others if danger is near. I believe the blue jays call is the general alarm for all species who visit the bird feedersIs it just a coincidence that their feathers are a military blue?
As for migration, the strength in numbers means that small errors in direction made by one individual can be corrected by the group’s memory. Birds also achieve more efficient and faster flight when they are flying in close proximity to others. There is the drafting effect, caused by the wind sweeping over one bird’s body and creating a slight vortex and vacuum behind it, as well as extra lift provided by their neighbor’s wings. To achieve this benefit, they should fly on the same horizontal plane with their wingtips as close as possible.
Ravens, hawks, owls and woodpeckers do not form flocks. All of these species tend to be more solitary. The fact that all of them are predators probably has something to do with it. And none of us will ever have the chance to see the greatest flock of birds ever seen in the U.S. – that of the Passenger Pigeons. I don’t know about you, but I feel cheated out of one of the world’s most amazing natural events. It was the Passenger Pigeon’s technique of living in large flocks that ensured its survival. By the time people realized how severely the birds were threatened, it was too late to save them. They could not exist in small flocks and did not know how to protect themselves from predators. They were a very beautiful bird and now they are just an entry in the history books.
I don’t like to think that something like this could happen again, even though we don’t have any flocks close to that size. But today nearly 12% of the world’s 9,800 bird species face serious threats to their survival in the next 50 years. We must be aware and educate ourselves about ways to protect habitat, since this is their first means of self-defense and preservation.
We can also help by keeping our feeders filled with an assortment of wild bird seed and birdfeeders. If you are lucky and weather conditions are right, you could see a flock of Common Redpolls, Pine Siskins, or Purple Finch yet this winter.