The siskin is most commonly mistaken for a greenfinch and visits gardens during winter and early spring. It is one of the smallest birds in the finch family and is even dwarfed by a goldfinch. It has a narrower bill than most finches and its tail splays outwards in two directions creating a fork.

The adult male siskin has a bright yellow face with olive cheeks and a black cap; its wings are predominantly black with a bright yellow wing-band which stands out amongst the black. The tips of its tail are black which fade to an olive colour before becoming a bright yellow on the male's back.

Female siskins are greener in colour and don't have the black cap exhibited by the male. They have a more mottled appearance with streaks on their tops and bottoms. Juvenile siskins have the same general appearance as that of the females but are brown in colour and look even more mottled.

Siskins will visit a garden that has peanuts on offer in the winter; this is because peanuts are a high energy food that is of great importance to their well-being in colder weather. Other high energy foods that siskins are likely to enjoy include sunflower hearts and suet products.