The Carlisle Mosquito Online

Friday, November 11, 2005

Features

Biodiversity Corner Dark-eyed Junco

photo by Sue Finnegan, certified master bander, Wing Island banding station on Cape Cod
Riddle: I know, I usually start with the name of the species but this week a riddle seemed appropriate. Why is a junco like a rhododendron? It has nothing to do with the fact that gardeners fondly refer to rhododendrons as rhodies. Birders do not refer to juncos as junkies. Both juncos and rhododendrons survive the winter in Carlisle but the rhodies don't fly north to breed. The answer to the riddle is that the common name is the same as the genus name. This happens quite often with plants (e.g. iris, geranium, hosta, etc) but seldom with birds. The dark-eyed junco (aka northern junco) is Junco hyemalis. There are several subspecies or races that used to be considered distinct species but are now all lumped together as Junco hyemalis. The race we see in Carlisle is known as the slate-colored junco. People in certain parts of the country (not in the northern breeding territories in Canada) refer to dark-eyed juncos as "snowbirds" because their arrival suggests the start of winter.

When and where seen: "Sanctuary," the journal of the Mass Audubon Society, routinely prints an outdoor almanac on the back cover. It gives an approximate date for plant and animal indicators of the changing seasons. In the fall issue, it said "first juncos arrive from the north" around October 12. Tom Brownrigg saw some juncos at the Cranberry Bog on October 16. He has recollections of early arrivals at Great Brook Farm State Park at the end of September. Juncos are common visitors to bird feeders. Last year, 197 were counted in the Carlisle Christmas bird count — see Ken Harte's graph for 32 years of Christmas bird count data.

Distinguishing characteristics: The slate-colored race of junco is smaller than a cardinal and larger than a chickadee. It is about the size of a tufted titmouse. The head, chest, and upper parts are dark gray. The female has some brown tinges in with the gray. The belly is white. The demarcation between the gray and the white is quite sharp — as if the junco stepped in a bowl of milk. The outer tail feathers are white, and the bill is pinkish-white and conical.

Food: The dark-eyed junco is primarily a seed eater but it eats insects in the breeding season and feeds soft-bodied insects to its nestlings. David Sibley describes a kind of Six Flags foraging method in which the bird alights at the top of a thin seed stalk and 'rides' it to the ground. It then holds the stalk down on terra firma and picks off the seeds.

References: David Allen Sibley, The Sibley Guide to Bird Life and Behavior; Patuxent Wildlife Research Center at www.mbr-pwrc.usgs.gov (search on "junco").


2005 The Carlisle Mosquito