For the Birds Radio Program: Pine Siskin
(Recording of a Pine Siskin)
People in Port Wing, Wisconsin, are all abuzz about Pine Siskins. Why are there so many? And why were so many other winter birds absent from feeders this year?
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 has been an exceptional irruption year for siskins. During fall migration, we counted 14,714 from the Lakewood Pumping Station migrating along the Lake Superior shoreline. And siskin numbers were still on the rise when we stopped counting in October. Unfortunately, there must have been larger seed crops for spruce, pine, and other conifers somewhere else, because most of the other northern finches were few and far between this season. A few people have had Pine Grosbeaks or Evening Grosbeaks, but not in big numbers. Some redpoll flocks have been large, especially late in the season, but not every feeder had them. Pne Siskins were by far the mst abundant and conspicuous feeder finch this year.
One other feature of these 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 during late winter–some listeners have already observed them carrying nesting materials around. 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.”