For the Birds: Fox Sparrow; Citizen Ornithology Science Opportunities

In the grand spectacle of the fall bird migration, the arrival of October signals the end of the migration of most warblers and other insect-eating birds. For songbirds, I think of October as the month of the sparrows. Relying on the seeds of grasses and other plants, sparrows can find sufficient food through the fall. There are slim pickings of caterpillars for warblers and other insect-eating birds now.

I keep a sharp eye on the ground these days, particularly below our bird feeders. I’m looking for a noticeably larger sparrow than the Song Sparrows that are so common now. The sparrow I am seeking is the Fox Sparrow, one of the largest sparrows in North America.

Our Fox Sparrows share with the Song Sparrow a strongly streaked breast. As befits their name, Fox Sparrows in the east have a strong reddish cast to their upperparts and head. These are handsome birds.

Although Fox Sparrows nest sparsely in the northwestern part of our state, most of the Fox Sparrows we see are passage migrants. That is to say, the birds nest to the north of us and winter to the south. We see them coming and going during their spring and fall migrations.

Fox Sparrows nest in a large swath across the northern portion of North America from Labrador in the east, across the Canadian provinces into most of Alaska. Breeeding populations are also found at altitude in the Rocky Mountains into Colorado and in the Sierra Nevada down to central California. The wintering ground is essentially the southeastern quadrant of North America with some wintering in the lowlands of California.

Audubon saw Fox Sparrows in Labrador in 1834. The Fox Sparrows in Labrador have the rufous feathering of the birds that pass through Maine. Audubon had no idea how variable Fox Sparrows are across their breeding range.

This striking geographical variation has resulted in the description of 18 distinct subspecies grouped into three or four larger groups. An ornithologist at the University of Minnesota, Robert Zink, has analyzed the DNA of Fox Sparrows from many of these groups. His results suggest that there may be as many as four species all currently called Fox Sparrows. Common names have been given to these distinctive forms: the Reddish Fox Sparrow of eastern North America, the Sooty Fox Sparrow that nests from the Aleutian Islands of Alaska south to Washington state, the Slate-colored Fox Sparrow that nest in the Rockies and the Thick-billed Fox Sparrow nesting from Oregon south to southern California.

I find Zink’s recommendation that Fox Sparrows be split into several species compelling. However, the American Ornithologists Union Check-list Committee, the body that approves all taxonomic changes of Western Hemisphere birds, is not fully convinced and so far Fox Sparrow is considered to be a single, highly variable species. Stay tuned; I expect Fox Sparrow will be split into several species in the not too distant future.

The different types of Fox Sparrows show markedly different migratory strategies. The Reddish Fox Sparrows have a long migration from northern Canada breeding grounds to wintering grounds as far south as the panhandle of Florida. Californian Thick-billed Fox Sparrows migrate only short distances, sometimes just descending the mountain that they nest on to spend the winter.

Despite the broad geographic reach of these sparrows, significant gaps in our knowledge of their nesting biology exist. On the breeding grounds, Fox Sparrows are somewhat shy. Furthermore, they tend to nest in short, dense shrubs making nest-finding and observations of parents at the nest extraordinarily difficult. Add to these factors the fact that Fox Sparrows tend to nest where human density is low.

Winter Bird Counts

It’s not too early to think about the joys of winter birding. Any Maine birder has two opportunities to participate in an organized winter bird count. The first is the National Audubon Society Christmas Bird Count, which will occur from December 14 until January 4. A list of the dates for many Maine counts can be found at: http://www.mainebirding.net/events/cbc

Birders of all skill levels are welcome. Find a count on the list above close to you and give the compiler a call or email to join up. We now have over 100 years of data on the abundance of birds in the early part of winter.

A second opportunity is The Great Backyard Bird Count, organized by the Cornell Laboratory of Ornithology and the National Audubon Society. This count will be held in the deep of winter on February 13-16, 2008. Participants count the birds at their feeders and report their counts online. To sign up for this valuable citizen-science project, visit http://www.birdsource.org/gbbc/

[Originally published on October 4, 2008]