Pine Siskins become considerably plumper through accumulation of fat with the onset of winter. Each bird can pack enough seeds into its expandable esophagus to support itself through five hours of rest at –4º F temperatures.
Pine Siskins have difficulty opening the large seeds of striped sunflower but enjoy black-oil sunflower seed, chips and Nyjer.
A siskin may take up a position near an Evening Grosbeak that is eating larger seeds like striped sunflower to pick up dropped particles and will even defend the position against other siskins.
Pine Siskins may nest in loose colonies and will tolerate the occasional visit to one another's nests after their young are hatched.
The Pine Siskin is the most common of the "winter finches" to be found at your feeders…but not every year. An “irruption” migration usually takes place every two or three years that can bring large numbers of Siskins to your backyard.
The Pine Siskin irruption migrations mainly occur when the seed crop has failed in the boreal forests. In some years large flocks may appear as far south as Florida.
Some “irruptive” Siskins may stay near a dependable food source and nest far south of the normal breeding range.
The primary natural foods of Pine Siskins are the seeds of hemlocks, alders, birches, and cedars.
Pine Siskins, like most northern finches, are fond of salt. They seek out natural salt licks and in the winter they can be found along highways eating the salt used to melt ice and snow.
Siskins, crossbills and other finches have been observed eating flaking mortar as a source of sodium and calcium.