A wave of tiny birds erupts at our bird feeders. They supplant the normal visitors, chickadees, goldfinches, pee wees, nuthatches, and cardinals. By sheer numbers they overwhelm both the other customers of this dietary dispensary and the supply of food within the feeders. In a matter of hours they empty six feeders, each holding a half of gallon of black sunflower seeds.
This invasion of redpolls is not unprecedented. It last occurred about five or six years ago. Like then, the available food in the boreal forest and tundra five to eight hundred miles to the north is inadequate. These many birds, which seem to act like one in a manner similar to honey bees, have vanquished the far north in search of reasonable food supplies. We seldom see a bird or two, rather they arrive in flocks of several hundred birds about twice a day. They gorge for about twenty minutes before retiring to the nearby forest. They always arrive and leave in a massive flock. It’s not like one or two scout birds arrive and go back to tell the others. No, there entrance is a flood of birds. They arrive in one wave, nearly empty all of the feeders, and exit like the same wave retreating from the beach.
Redpolls feed primarily on seeds in the cooler seasons. There favorite food appears to be white and gray birch seeds, poplar seeds, willowm and alder seeds. They also dine on tamarck seeds. The far north is chuck full of these tree and shrub species. These deciduous plants are uniquely adapted to the northern climates. The tree’s shrub’s entire identity is dominated by evolutionary tricks that allow them to live in these severely cold climates. Some might consider them the Nanooks of the plant kingdom. But every once in a while climatic conditions limit seed production. Unexpected cold during their flowering period, drought, and severe storms can all limit their progeny. This past summer must have held one of these events. There is little viable seed in the boreal and tundra deciduous plant community. And the birds have left for greener pastures, so to speak.
These mass exoduses are known as irruptions (no, not eruptions). Redpolls are not the only birds to leave in large flocks. Pine siskins, purple finches, white winged crossbills, and pine grosbeaks will do the same. These bird species are highly dependent, during the winter months, on these massive seed supplies that are usually plentiful in the far north. Like all foraging it is a matter of locating and gathering sustenance for energy. Without the sustenance to keep them warm the red polls would perish in the extreme climates of the boreal forest and tundra.
Redpolls are unique amongst the finch family. Their tiny size allows them to subsist on a frugal diet. They rely on large flocks to survive. The “many eyes” of a flock helps them to locate each and every food source within a given area. The flock seems to operate as one organism. Red polls also are well adapted to cold climates. Like many small birds they can ruffle their feathers to trap air and insulate their tiny bodies. In extreme cold they will dive into the snow. There the temperature can stay just at or slightly below freezing when the air temperature is well south of thirty below zero (Fahrenheit).
Perhaps the most unique adaptation that the red polls possess is their esophageal diverticulum. This unusual feature is a small pocket situated in their neck. Redpolls use the esophageal diverticulum to store seeds. By having a food supply “to go” during a storm or an extreme cold period they can have a ready supply of energy while sheltered from inclement weather. .They regurgitate the seed when ready to consume them allowing them extended consumption without an expenditure of energy. Energy conservation is the most important aspect of survival in extreme climates. Without energy conservation many of these species would perish.
Interestingly, redpolls are not aggressive. When they invade a feeding station or feeding location they do not chase other bird species away. Both blackcapped chickadees and goldfinches seem tolerant of these mass entrances although some shy individuals may exit temporarily. They feed amongst the many redpolls, competing for food the best they can. They seem to know that the redpolls won’t stay long. After gorging for twenty minutes or so the redpolls all leave at once when they fly off to some not too far off tree where they seem to enjoy each others company.
Redpolls are best identified by the small red cap on the top of their heads. The males often have a reddish wash of colors on their chest as well. They are about the size of a chickadee and nearly always in a large flock. During the summer months they enjoy the long days of the far north. During the warmer season they consume part of the large flying insect population; a seemingly never ending food supply in these northern latitude environs!
As I watch these little critters eat enormous amounts of bird food at our feeders I feel a sense of wonder. That they are just outside of my window is marvelous. That they choose to visit our bird feeders is just reward for our bird feeding habit.
And when they leave to head back north they will do so just as suddenly as they came. One day they will be here and the next day they will not.
I’ll envy their trip to the boreal northern sections of Canada. I won’t be taking mine until summer.
Written for www.wildramblings.com in January of 2013.