The three species are:
The Arctic Redpoll, Carduelis hornemanni (subspecies C. h. hornemanni and C. h. exilipes)
The Common Redpoll, Carduelis flammea (subspecies C. f. islandica and C. f. rostrata)
The Lesser Redpoll, Carduelis cabaret

See also Goldfinch

  
www.ecosystema.ru ®
They are primarily seed-eaters, and often feed acrobatically like a tit; their diet may include some insects in summer.
They have a dry reeling song and a metallic call.
They lay 4-7 eggs in a nest in a tree or, in the case of Arctic Redpoll, a large bush.
They can form large flocks outside the breeding season, sometimes mixed with other finches.
The redpoll, which is not - as the norwegian name indicates: Grey Redpoll - is not as grey, at least not the male, and neither the eggs.
They often form flocks during winter, and you may see them hanging donw from the tip of thin birch-branches.

  
Gråsisik, Common redpoll, Acanthis flammea
www.ecosystema.ru ®
All redpolls are northern breeding woodland species, associated with birch trees. They are small dumpy birds, brown or grey-brown above and with a red forehead patch. The adult male's breast is washed in red, but in females and young birds the buff breast and white belly are streaked with brown. The bill is small and yellow. Some birds, particularly young ones, are difficult to assign to species
Text above from Wikipedia, the free encyclopedia


Carduelis flammea
© Arthur Grosset

Lille gråsisken, Carduelis cabaret. D. 25.05.2005 Photo: © Svend Ove Jensen
Lesser Redpoll

Lille gråsisken, Carduelis cabaret. Lystbådehavnen i Sønderborg, d. 22.05.2001 Photo: © Svend Ove Jensen

Lesser Redpoll, Carduelis cabaret
Brownish streaky (often very bright) on top of tail, strong streaked brown back, streaked light brown breast and flanks, black mask around the bill, red on top of a brown head, and a white bar on the wings.
The Lesser Redpoll breeds in the British Isles, around the Alps and the North Sea from northern France to south-east Norway.
It has spread in the last 50 or so years into southern Scandinavia and this has led to its recognition as a species in its own right.

Common Redpoll, Carduelis flammea
Greyish brown strong streaked breast, red and light streaked breast, streaked flanks, light bellow, red on top of head, black mask around nose, white bar on wings. All this means it is very like the other Redpolls.

Previously, The Lesser Redpoll was treated as a subspecies of Common Redpoll Carduelis flammea but this expansion brought
the two subspecies cabaret and flammea into direct contact. When this happened, it was observed that the two subspecies did not
hybridise and the subspecies were split.
The reference for this is "The taxonomic status of Lesser Redpoll" 2001 by Alan Knox et al. in British Birds, 94: 260-267.

Compared with Common Redpoll, Lesser Redpoll is significantly smaller and has richer plumage tones. Vocalizations are also slightly different. How it is compared to the other Carduelis-birds I don't know. Why don't I know? Well, just look below: