The pine siskin (Spinus pinus) is a North American bird in the finch family. It is a migratory bird with an extremely sporadic winter range. These birds are fairly small, being around the same size as the widespread American goldfinch. In both sexes, total length can range from 11–14 cm (4.3–5.5 in), with a wingspan of 18–22 cm (7.1–8.7 in) and weight of 12–18 g (0.42–0.63 oz).
Adults are brown on the upperparts and pale on the underparts, with heavy streaking throughout. They have short forked tails. Their bills are conical like most finches but are more elongated and slender than those of other co-occurring finches. Variably, pine siskins have yellow patches on their wings and tails, which may also consist of white streaks on the wings. Although they can be confused by the more inexperienced for other finches or even American sparrows, pine siskins are distinguished by their heavy streaking, relatively slender bills, notched tail, yellow or whitish patches on the wings and smallish size.
These birds forage in trees, shrubs and weeds. They mainly eat seeds, plant parts and some insects. In winter, they often feed in mixed flocks including American goldfinches and redpolls. Small seeds, especially thistle, red alder, birch, and spruce seeds, make up the majority of the pine siskin's diet. In a part of their esophagus called the crop, the species can store up to 10% of their body weight in seeds overnight, providing extra food on cold days. They will alternately eat the young buds of willows, elms and maples, and the soft stems and leaves of weeds and even young garden vegetables. They'll glean the seeds of grass, dandelions, chickweed, sunflowers and ragweed. Bird feeders often attract pine siskins, where they may eat fragments of heavy-shelled seeds, such as black oil sunflowers, left behind by heavier-billed bird species. In summer, they will eat many insects, especially aphids, as well as a few spiders and grubs, which they then feed to the young as a protein-rich food that contributes to their growth. By the time of winter, even first year siskins predominately eat seeds.
Pine siskins can survive in very cold temperatures. The metabolic rates of this species are typically 40% higher than a "normal" songbird of their size. When temperatures plunge as low as −70 °C (−94 °F), they can accelerate that rate up to five times normal for several hours. They also put on half again as much winter fat as their common redpoll and American goldfinch relatives. They also can protect their young from cold as well. Nests are often heavily insulated with thick plant materials and females may literally never cease incubating their eggs and hatchlings, while being fed by their male mate.
(lat. Spinus pinus)
