Friday, April 3, 2009
If you have a thistle feeder in Carlisle, there is a good chance that it has been frequented this winter by a relatively uncommon bird in these parts, the Pine Siskin. The Pine Siskin is a member of the finch family, closely related to the goldfinches, and from a distance it can
easily be mistaken for a winter-plumaged American Goldfinch. It is of similar size and shape, and a drab-looking brown color. Seen close-up, or through binoculars, the differences are readily apparent: the siskin looks slightly darker overall, but is heavily streaked brown and white, the bill is thinner and more pointed. There is usually a touch of yellow on the edges of the wing feathers and the base of the tail and the males have a yellow bar on the wing. They will become easier to distinguish as the goldfinches molt into their brighter breeding plumage.
The Latin name is Carduelis pinus. The genus name Carduelis (which also includes goldfinches) is derived from Carduus, meaning thistle; pinus, as you probably guessed, refers to Carlisle’s signature tree. So the name means something like “pine-dwelling thistle-eater,” a pretty apt description. They are usually found in the boreal coniferous forests and feed mainly on a variety of seeds, but have a special affinity for Niger thistle seed.
Massachusetts is south of the Pine Siskin’s normal range, which includes northern New England and southern Canada. They are not migratory in the conventional sense, but their winter travels are very erratic. Sometimes they stay up north and hardly any are seen at all, other years large numbers move into our area and are seen throughout the winter, often in sizable flocks. This large influx is known as an irruption, which means invasion, and is characteristic of a number of northern species such as Crossbills and Redpolls as well as Pine Siskins. The large winter movements are generally triggered by food shortages, the result of a failure of the northern seed crop. The effects are often magnified by a bumper crop the previous year having swelled the population, further increasing pressure on food resources. The increased popularity of bird feeding is significant: it provides a dependable source of food when natural sources may not. This winter has seen a significant irruption of northern finches, particularly Crossbills and Siskins.
These patterns are evident in the Carlisle section of the annual Concord Christmas Bird Count. Starting in 1973, no Siskins were found in 21 of those 36 years. The highest count was 137 in 1977, a major irruption year, the only year that Pine Grosbeak was recorded, and one of only two when White-winged Crossbill has appeared in the Carlisle count. The 2008 count of 40 was the third highest. Pine Siskins breeding in Massachusetts were virtually unknown before 1970, but since that time breeding reports have become more common in summers following a winter irruption, particularly in 1978. There are early indications that 2009 may be another good summer for breeding Siskins.
Around March 7, I started to notice “my” Siskins being more vocal. Their song is a jumbled chatter, but it has a very distinctive part: a drawn out, buzzy zrreeeee, rising in pitch (the birds from Canada reportedly go zrreeeee….eh). On the glorious sunny afternoon of the 15th, I sat on the patio watching a pair chowing down on the thistle seed, and followed them with binoculars as they flew up for a dessert of red maple buds. Several times, I observed one bird (the male) feeding its mate, in a ceremony not unlike the groom feeding wedding cake to his bride. This is a well documented courtship behavior of Siskins (and many other birds), and is a good indication that they may well nest locally. On March 23, Tom Brownrigg observed a pair stripping bark from tree branches on North Road. There have also been several reports on the Massbird web site of nesting behavior in other towns around the state.
Their nests are shallow saucers of bark and twigs, well hidden on branches high in coniferous trees. The males continue to feed the female while she incubates 3-4 eggs. If Pine Siskins are indeed breeding locally, we can expect some fledglings around our feeders in early May. Keep your eyes peeled!
References: Massachusetts Breeding Bird Atlas, edited by Wayne R. Peterson and W. Roger Meservey, Massachusetts Audubon Society, 2003; The Sibley Guide to Birds, David Allen Sibley. Alfred A. Knopf, 2000; The Birders’ Handbook, Paul R. Ehrlich, David S. Dobkin and Darryl Wheye. Simon & Schuster Inc., 1998; www.massbird.org. Thanks to Ken Harte for sharing his Christmas Bird Count data. ∆
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