Irruption Year: Redpolls breed as far north as Greenland and Nunavut and as far west as Alaska where they feed on grasses and the seeds of pine, birch, alder and spruce. Seed production of these trees is dependent on the climate of the previous years, spruce trees for example produce more cones after two summers with heavy rainfall and winters with low snowfall preceded by one dry year. To make the most of these plentiful years, some species will have extra clutches of eggs or litters as the odds of survival are much higher. Dryer conditions over a long period of time can result in fewer seeds grown, meaning less food for finches like the redpoll. In order to find enough food, these birds, along with other seed specialists, will migrate south in larger numbers than normal. During these irruption years, common redpolls can more easily be found further south, in such areas as Ontario, compared to previous years. Even hoary redpolls, rarities for the region, have been observed in larger numbers.
Sources:
Mandelbaum, Ryan F. "This Winter Marks an Incredible "Superflight" of Hungry Winter Finches." Audubon, 11 Dec. 2020, www.audubon.org/news/this-winter-marks-incredible-superflight-hungry-winter-finches. Accessed 10 Dec. 2021. |