Common Crossbill Bird is a stocky finch comparable to a Greenfinch in build, with a thick neck and largish head. The bill has elongated tips to the mandibles, which cross over an adaptation for prising seeds out of conifer cones. The tail is rather short and deeply cleft, visible in the undulating flight. Males are red all over, except for dark brown wings and tail and a pale vent. Females are grey-green, diffusely streaked on the mantle and yellower on the rump. Young birds are grey-brown and streaked all over. This species closely resembles both the Scottish and Parrot Crossbills, so attention must be paid to the voice and also to the bill, which in the Common Crossbill is longer than it is deep, with a gently curved culmen.
Common Crossbill Bird is a resident and widespread, although rather localized and highly irruptive, travelling long distances when new food sources are required. It is found exclusively in conifers, and has a preference for spruce. In Britain it is found in scattered pockets of suitable habitat, such as upland areas of Scotland and Wales and conifer-forested parts of England.
Common Crossbill Bird is often vocal. The calls can be divided into flight and excitement calls: the 'flight' call (not necessarily given in flight, however!) is a fairly loud and explosive repeated "glipp glipp. or "chlip chlip chlip"; the 'excitement' call is a deeper, highly infectious call, repeated excitedly, and can be described as "chuop, choup..." or "chuk, chuk...". It also gives a downward-inflected "tchi'choo tchi'choo" call. The song is a fairly slow collection of call notes, whistles and nasal trills, interspersed with some higher "chiree chiree" sounds, such as "chiree chiree chiree chup-chup-chup chue cheu cheu dzhirrroo dzhirrroo chip chip chiree chiree tup tup tup...", etc. Recent studies have shown that there are as many as seven different 'cryptic' forms of Common Crossbill occurring in north-western Europe, all with subtly different calls.