Back in the early 1970s, the Siskin was an unfamiliar species to many birdwatchers, restricted as a breeding species to Scotland and to those areas with large conifer plantations within England and Wales. However, it is now a familiar winter visitor to many garden bird tables away from the expanding breeding range. In fact, the breeding population has increased to such an extent that the species is now reported from 1 in 10 gardens in any given week during the summer months - see here
The Siskin is one of our smallest finches (smaller than a Goldfinch). It has a relatively long and narrow bill for a finch and also has a distinctive forked tail. The plumage is predominantly a yellow-green colour, with a striking yellow band on the wing and yellow patches at the base of the tail. Adult males have a black crown and a lot of black in the wing, which contrasts with the yellow wing-band. Females are greener in colour than the males, streaked above and without the black crown. Juveniles resemble females but are buff-brown above and more heavily streaked (both above and below).
The breeding range of Siskins within Britain has expanded following the spread of new conifer plantations. This, coupled by the exploitation of peanuts provided in gardens, has resulted in a dramatic increase in the number of Siskins visiting gardens during the late winter months. Almost invariably it is after the New Year that Siskins begin to be reported in increasing numbers in gardens. In spring, there is a rapid movement of birds away from gardens and back to the breeding areas. Birds continuing to visit gardens during the breeding season will be local breeders, with adults accompanied by young a feature of late summer in these areas.
Movements into gardens are, in part, determined by the size of natural seed stocks. An examination of BTO Garden BirdWatch data revealed that garden use was greater in those years when the Sitka Spruce seed crop was poor than in years when it was good (McKenzie et al. 2007).
A similar thing can be seen at the micro-scale, with movements into gardens more evident on wet days (when the cones remain closed) than on dry days (when the cones open).