Where I live (Alberta), the bird diversity decreases quite dramatically during the winter. Warblers, flycatchers, thrushes, shorebirds, and most waterfowl head south for the winter. However, the birds that do stay behind include chickadees, creepers, woodpeckers, nuthatches, waxwings, ravens, grouse, most owls, jays, and magpies, so the birding is still good. Some finches, merlins, juncos and kinglets stick around too. Common Goldeneyes, Mallards, and Canada Geese will also tough out the winter in areas where there is open water, such as where treated sewage effluent keeps areas of rivers and lakes warmer than normal. A few Bald Eagles will stick around and hunt the waterfowl, and eagles hunting ducks and geese can sometimes be seen right in Lethbridge, Calgary, or Edmonton.
There are also some species that show up in Alberta only in the winter and they make winter birdwatching quite interesting. These northern birds nest in the Arctic and often head south in winter in search of food. Such birds include Snowy Owls, Rough-legged Hawks, and redpolls. Redpolls are members of the finch family and there are two species: the Common Redpoll and the Hoary Redpoll. The two species look alike, although hoaries are paler overall and have white rumps.
Redpolls are birds of the north. Common Redpolls breed in Alaska, Nunavut, the Northwest Territories, the Yukon, and northern Ontario, Quebec and Manitoba. In Nunavut, they breed on the mainland and southern Baffin Island. Hoary (AKA Arctic) Redpolls nest even further north, in northern Alaska, Greenland, and the northern parts of Canada’s three territories, including northern Baffin Island and Ellesmere Island (the northernmost of the Arctic islands). Common and Hoary Redpolls also occur in northern Europe and Asia.
Many redpolls do head south in winter, not necessarily to escape the cold but to search for food. Many spend the winter in central and southern Canada. However, some still overwinter as far north as central Alaska, the Yukon and Northwest Territories. In years where redpoll numbers are high and there is a lack of small tree seeds (such as birch seeds) up north, they may start to show up as far south as the central United States in search of food. These influxes of redpolls into the central USA are referred to as “irruptions.”
When and where the redpolls show up varies from year to year. While many migratory birds breed and overwinter in the same areas each year, redpolls are wanderers. A redpoll that overwintered in the north one year may head thousands of kilometers south the next year and some will fly thousands of kilometers in one year. For example, a Common Redpoll banded in Belgium was later captured in China, 8350 km away. Another Common Redpoll banded in Fairbanks, Alaska during one winter was recaptured 5000 km away in Montreal, Quebec the next winter – a very impressive journey for such a small bird!
Redpolls will happily visit feeders and they particularly like black Nyger (or “Niger”) seeds. So, if you live in Canada or the northern US and want to see redpolls, try putting out a feeder stocked with Nyger seeds in winter. If there aren’t any redpolls in the area, you may still attract other finches, such as Pine Siskins. Like redpolls, Pine Siskins are finches that wander North America and migrate in response to varying food supplies.
Redpolls are very tough birds and can tolerate extremely low temperatures. After all, temperatures can dip to -45 C even in their ‘southern’ winter ranges. This is particularly impressive since these birds are small – without the feathers, they’re about the size of a human thumb. They also have to go twelve or more hours without eating during long northern nights. Most small birds need to eat frequently because of their high metabolic rates. So, how do redpolls withstand northern winters?
First, to help them make it through long nights, redpolls have an extra pouch in their throats (besides the crop) to store seeds in. The seeds can then be used as a fuel source throughout the nights. A redpoll can store up to 2 g of seeds in its pouch, and considering that redpolls are only 10-12 g, that is a lot of food! Besides Nyger seeds from feeders, they often feed on birch, alder, or aspen seeds.
Redpolls and other northern finches can also reduce the amount of energy they use at night by undergoing a process called ‘controlled hypothermia.’ During the night, redpolls with low fat reserves may also undergo a drop in body temperature by about 10 °C. Chickadees and House Sparrows do this as well. The reason they drop their temperatures is to conserve energy. The birds will use less energy to maintain a body temperature of ~ 30 C than a body temperature of ~ 40 C. The disadvantage is that they cannot move around well with such a low body temperature, but that doesn’t matter too much when they are sleeping.
Redpolls and many other small northern birds will also ‘clump’ together in tree cavities – or snow tunnels – to conserve heat. Redpolls in particular often tunnel into the snow to stay warm. On very cold days and nights, the ‘subnivean space’ (area under the snow) may be many degrees warmer than the area above the snow. Ptarmigan and grouse will also rest underneath the snow to stay warm. At rest, redpolls will also fluff up their feathers to trap air between them. The extra air trapped between the feathers does add some extra insulation. Additionally, redpolls will grow very thick coats of down before the winter season.
For me, redpolls mark the coming and going of winter. They tend to show up where I live in December, and head out by March or early April. I usually manage to see some every year and some years they absolutely inundate my backyard feeders. They definitely make winter birdwatching much more interesting as they can only be seen in the winter in many areas.
(Jan. 12 2014 edit: This year does not seem to be an irruption year. Very few redpolls showed up on bird counts in Alberta and some regions had none at all!).
Groth, J. 2001. “Finches and Allies.” In: The Sibley Guide to Bird Life and Behavior.” Elphick, C., Dunning, J. B. Jr., and Sibley, D. A., Eds. Alfred A. Knopf, New York, NY.
Newton I. 2006. Advances in the study of irruption. Ardea. 94: 433-460.
Reinertsen R. E. 1983. Nocturnal hypothermia and its energetic significance for small birds living in the arctic and subarctic regions. A review. Polar Research 1 n. s. 269-284.