Common Redpoll

Scientific Name	Acanthis flammea
Survival Strategy	Medium-distance migrant
Arrival in Upper Midwest	Late December
Departure	Mid-March through April
Destination	Arctic, Subarctic
Conservation Status	Least Concern

Phenology

Spring
Common redpolls leave for their breeding grounds in the taiga and tundra of northern Canada from mid-March through April. The timing of the first clutch of 4 to 6 eggs is dependent on local weather conditions and ranges from late April to early June. The female will incubate the eggs for 11 days, after which the young are born nearly naked, blind, and helpless (altricial). The young leave the nest 11 days after hatching and at 13 days can fly well enough to follow their parents.

Summer
Redpolls will often attempt a second brood in mid-summer. By August, small pre-migratory flocks start to form.

Fall
In September and October, flocks of common redpolls will begin to leave their breeding grounds, typically moving south until they find a reliable food supply.

Winter
Common redpolls are irruptive winter visitors to the upper Midwest and typically arrive in December. The timing and number of birds depend on the quality of the seed crops on birches, alders, and spruce in Canada. When seeds are scarce, redpolls will move further south to find food.

Behavior

Snow Tunneling
In the Arctic, redpolls will tunnel into soft snow to protect themselves from brutal winter temperatures; however, redpolls that winter in the upper Midwest do not rely on this behavior. In the northern portions of the redpoll’s range, the snow rarely thaws and maintains its loose texture. The air spaces between the snow crystals increase the insulation value and ensure that any birds taking refuge in the snow can make a quick exit in the morning. In contrast, the frequent thaws of this finch’s more southern winter range create an icy coating on the surface as nighttime temperatures drop below freezing, which would trap these tiny birds.

The Value of a Crop
Before sheltering in dense conifers (or snow tunnels) for the night, redpolls will forage for high-calorie seeds, storing the food in their crop, then digesting it in the relative safety of their roost. A crop full of seeds ensures a fuel supply needed to survive the cold, like the stack of firewood many people keep next to their woodstove.

Physiology

Thicker and Heavier Coat
The common redpoll, a bird that at 15 grams is about as heavy as a compact disk, can survive temperatures down to -50°C (-58°F), colder than any other small songbird. Redpolls increase the mass of insulating feathers before winter by more than 30%, much like adding a heavier blanket to your bed in winter.

By fluffing their feathers (piloerection), redpolls can trap more air next to their body and prevent heat from escaping. In the same way, a quilted “puffer” jacket traps more air and keeps outdoor enthusiasts warm in winter.

Diet

Redpolls prefer the seeds of birches, alders, and spruce. They eat 31 to 42% of their body mass every day depending on the season. In summer, they add spiders and insects to their diet.

Most finches, including common redpolls, are fond of the “thistle seed” used in many bird feeders. The seed comes from the African yellow daisy (Guizotia abyssinica) and is unrelated to true thistles. The plant is grown commercially in Africa and India for cooking oil and birdseed. To prevent the mispronunciation of the word, the Wild Bird Feeding Institute trademarked the name “Nyjer®” in 1998.

The Finch Research Network, a group that works to study and protect finch species, releases an annual winter finch forecast. This group methodically surveys the cone or catkin production of each finch species’ preferred seed crop. By using data from trees throughout their range, researchers can predict if and when the birds will need to move south to find food.

Lifespan and Mortality

Common redpolls live about 2 to 3 years. Using bird banding data, researchers documented a redpoll in Europe that was at least nine years old.

Predators
Predators of adult redpolls include peregrine falcons, merlins, and domestic cats. Red squirrels and gray jays will prey on eggs and young chicks.

Diseases
Salmonella is easily transmitted at dirty bird feeders and can be lethal to winter flocks of common redpolls. Regularly disinfecting bird feeders can help prevent the spread of this deadly bacteria.

Climate Vulnerability

The range of common redpolls will likely shift out of the lower 48 states and be reduced in size by 40% due to a warmer climate.

Never Stop Learning

World Travelers: A common redpoll banded in Michigan was recovered in eastern Siberia, while another redpoll banded in Belgium traveled to northeastern China.

References

Finch Research Network: Winter Finch Forecast https://finchnetwork.org/winter-finch-forecast-2021-2022-by-tyler-hoar

Lawrence I. Grinnell. “Nesting Habits of the Common Redpoll.” The Wilson Bulletin, vol. 55, no. 3, Wilson Ornithological Society, 1943, pp. 155–63, http://www.jstor.org/stable/4157260.

Knox, A. G. and P. E. Lowther (2020). Common Redpoll (Acanthis flammea), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.comred.01

How Climate Change Will Reshape the Range of the Common Redpoll https://www.audubon.org/field-guide/bird/common-redpoll

Animal Life Expectancy: Common Redpoll https://www.worldlifeexpectancy.com/bird-life-expectancy-redpoll

Sick Birds and Bird Diseases – FeederWatch https://feederwatch.org/learn/sick-birds-and-bird-diseases/

Boreal Songbird Initiative: Common Redpoll https://www.borealbirds.org/bird/common-redpoll

Heinrich, Bernd. “Redpoll Snow Bathing: Observations and Hypothesis.” Northeastern Naturalist, vol. 21, no. 4, Eagle Hill Institute, 2014, pp. N45–52, http://www.jstor.org/stable/26453831.

Wild Bird Feeding Institute https://www.wbfi.org/

Brooks, William S.. “Comparative Adaptations of the Alaskan Redpolls to the Arctic Environment.” (2016). https://sora.unm.edu/sites/default/files/journals/wilson/v080n03/p0253-p0280.pdf

White CM, West GC. The annual lipid cycle and feeding behavior of Alaskan redpolls. Oecologia. 1977 Sep;27(3):227-238. doi: 10.1007/BF00347468. PMID: 28308974.