“V’s” of migrating Canada Geese are a common sight and sound in the Northeast during October. The inevitable question arises: why fly in a V formation? In part, because it conserves energy. But exactly how does it do this?
As the lead goose flaps, it creates tiny vortexes (circular patterns of rotating air) swirling off its wings as well as into the space behind it. The vortex behind a goose goes downward, while the vortexes on either side of its wings go up. If a goose flies directly behind the goose in front of it, air will be pushing it down. If it flies off to the outer side of the goose in front of it, air is pushing upward and the goose will get a slight lift, making flying easier.
Picture two geese flying behind and to the outer sides of the lead goose. Additional geese, in order to avoid the vortex behind the lead goose as well as the vortexes directly behind the next two geese, will fly behind and to the outside of the wings of the two birds in front of them, getting a lift and forming a “V.”
Because the lead goose has no vortex to get a lift from, it tires more easily than the other geese. It periodically falls back and is replaced by another goose in the formation. This cooperative process of taking turns leading the flock minimizes the need for the birds to stop and rest.
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My apologies to the 50+/- NC readers who responded with great creativity to the latest Mystery Photo! The photographer and I had a miscommunication, and I misdirected readers about the actual mystery you were to solve! I thought the photographer had observed a goose making the two parallel lines in the ice with their feet (nails) as they landed. However, these two lines are actually just cracks in the ice, as many readers guessed (Susan Cloutier was the first to correctly identify them). While Canada Geese do use their feet as well as their wings as brakes to slow themselves down before they land and they do have a hind toe which conceivably could scratch the ice, the landing imprints of the geese (and what I should have asked readers to identify) are actually in the upper half of the photo (see red circle) where the snow has been plowed aside, revealing the darker ice underneath. The presence of a considerable amount of goose droppings confirms the identity of the birds landing on the ice.
Observers often ask how Canada Geese or other waterfowl can stand for long periods of time on frozen lakes and ponds.The legs and feet of waterfowl play an important part in maintaining their body temperature. In the summer, their large, flat feet cool their body by releasing a good deal of heat. In winter, the heat exchange system (counter-current circulation) in a bird’s legs prevents a great deal of body heat loss due to the fact that the warm arterial blood going into the bird’s feet is cooled by the colder blood traveling back to the body in adjacent veins. Constricted blood vessels in their legs further conserves heat. (Photo by Mike Hebb)
If you are fortunate enough to have a beaver pond near you, you should give the lodge more than a cursory glance this time of year. It is common to find Canada Geese nesting on beaver lodges, for obvious reasons – safety from most land predators. While Common ravens have been known to raid Canada Goose nests for eggs and goslings, the overall rate of survival of the goslings of lodge-nesting geese is very high.
A Canadian study showed that ponds with beaver lodges (and therefore Beaver activity which warms the water and thaws the ice) thaw at least 11 days sooner than ponds without Beavers, allowing early access to water for Canada Geese returning for the spring nesting season. Battles between pairs of geese vying for these coveted nesting sites are not uncommon.
Canada Geese have much to thank Beavers for. Not only can geese get an early nesting start on beaver lodges, they have a relatively safe spot to incubate their eggs and raise their young.
Within 24 hours of hatching, downy Canada Goose goslings leave their nest and are capable of walking, swimming, diving and feeding themselves. Like many species of waterfowl, their growth is rapid. Contour feathers on their wings and tail begin to emerge in about three weeks (note wing feathers of gosling in photo). Feathers on a gosling’s head, neck and back are the last to appear. Just before a gosling develops the ability to fly, the last fluff of down, which is on top of its head, disappears.
This is the time of year when the honking of migrating Canada Geese can be heard as the familiar V-shape formation passes overhead. Many of these birds have a long, arduous migration and they need to conserve as much energy as possible. The V-formation that they fly in enables them to do so, in that it greatly boosts the efficiency and range of flying birds. Geese flying in a V-formation have slower heart beats than geese flying solo, and they can achieve a distance of 71% greater than single birds. The birds in front make this possible by enduring the most air resistance and, at the same time, improving the aerodynamics of the birds behind them by reducing the drag by up to 65 percent. The geese are constantly rotating positions in order to share “flight fatigue.”
All North American birds replace their old, worn plumage with new feathers at least once a year, a process known as molting. Most birds have what is called a “sequential molt,” in which their flight feathers are lost one at a time (from each wing). This allows many birds to continue flying while molting. However, during their annual molt, waterfowl undergo a “simultaneous wing molt,” losing all of their primary wing feathers at once, preventing them from being able to fly for a month or more while their new primaries are growing in. During this period, they are extremely vulnerable, as this photograph testifies to. If you look closely at the remains of the Canada Goose’s wing on the right in the photograph (dark feathers), you’ll see that the new primaries have almost, but not quite, grown out of their sheaths, making them not yet functional. It’s apparent that this bird was unable to take flight during its molt in order to escape its predator.