Laura Erickson's For the Birds

(Recording of a Pine Siskin)

People in the Northland are all abuzz about Pine Siskins. Why are there suddenly so many?

Pine Siskins belong to a family called “Fringillidae.” This used to be a much larger family, until ornithologists split it into two groups. Now North American sparrows, cardinals, Rose-breasted Grosbeaks and other strongly territorial finches are placed in a new family called Emberizidae. The northern finches–the crossbills, redpolls, Pine Siskins, goldfinches, Pine Grosbeak, and Evening Grosbeak–are in the Fringillid family because they show some unique habits and because these birds have only 9 primary wing feathers–the Emberizid finches have 10.

Pine Siskins and other Fringillid finches are all “irruptive” species–that means that they live in big flocks which move about irregularly following food supplies. These birds are all seed eaters, and unlike just about all other songbirds, they even feed their nestlings seeds. All the fringillid species have fairly heavy beaks with special adaptations inside for holding and shelling seeds. Each seed is wedged in a groove at the side of the palate. When the lower jaw closes on it, the force crushes the seed. Then the husk is peeled off by the tongue and spit out, releasing the kernal to be swallowed. The bills of all North American finches are also adapted for extracting seeds from the seed heads of plants. Pine Siskins have an especially slender, tweezer-like bill for probing into thistles. That’s why this species is so partial to thistle and niger seed at feeders.

This year is shaping up to be a good irruption year for siskins. I’ve been hearing from people all over about siskin flocks visiting feeders.

One important feature of irruptive finches is that their breeding cycles don’t follow the same rhythms of other birds. They breed when their food sources are most abundant. Goldfinches breed at the end of summer when the down of thistle plants is available for lining their nests. Pine Siskins, which also eat a lot of conifer seeds, can start nesting even during winter, though seldom before February or March. They feed their babies regurgitated seed, so one parent can keep the eggs or young warm while the other flies off to fill its crop with food. Siskins don’t break up their flocks to breed, and they don’t defend much territory against other siskins. Unlike the songs of most birds, a siskin song isn’t a territorial warning–it’s just a siskin’s zippy way of singing “Let’s Get Physical.”

(Recording of a Pine Siskin)

This is Laura Erickson, and this program has been “For the Birds.”