For several years I have kept track of the number of birds and species here in our garden. Weekly, since 2014, these observations have been published here. The Redpoll is probably the most common bird in the garden and in February in recent years there have sometimes been up to 140 Redpolls here at the same time. This winter, however, has turned out to be quite different. The number of Redpolls has dropped dramatically. On average in February there have only been around 13 Redpolls here daily. The same goes for other places where feed is put out here in the Southwest.
Fluctuations in population sizes from year to year are normal and are more a rule than an exception. The reasons can be various, such as shortage of food, diseases, migration or a combination of these. Redpolls are not migrators but since their main food source, birch seed, was scarce last autumn they may have opted to migrate and will possibly return next spring.