The white-crowned sparrows must be wondering about our strange weather. Last October, near the end of their fall migration, they were met here by a heavy snowstorm. For the first time I can remember, we even had a white-crown at our feeder area from October 31 through November 2.
Usually, I see them during their spring migration in May when one appears almost like clockwork eating the dandelions gone to seed in our yard. And sure enough, during the heat wave in early May, one appeared to eat dandelion seeds on May 3 and 4. I thought that was my one look for the year at this spiffy bird—its two broad black head stripes neatly separated by a white stripe—when it or another white-crown, appeared on our driveway near dusk on May 11, feeding peacefully on weed seeds along with a small rabbit.
Would or wouldn’t it show up the following day when I was in the midst of my Pennsylvania Migratory Count? It waited until I was resting in the afternoon on the veranda to fly into a tulip tree sapling beside me. But it also appeared at the same time and place with the bunny as I concluded my count, proving that sometimes nature does repeat itself.
Why all the fuss and bother over seeing this species? Here in Pennsylvania it is only a migrant bird, passing quickly through our state in spring to reach its boreal nesting grounds in northern Ontario, Quebec, Newfoundland and Labrador. One white-crown, banded by Ralph K. Bell at Clarksville, Pennsylvania, on May 6, 1962, was recaptured 1,500 miles to the north at Battle Harbor, Labrador, on June 12, having averaged 40 miles a day. (Bell, incidentally, who is now 97, still leads bird clubs around his Greene County farm.)
The white-crowns migrate even faster heading southwest to central Texas and the lower Ohio Valley for the winter using, some researchers believe, the stars to navigate or some geomagnetic navigation because they have found slight amounts of the mineral magnetite embedded in the facial tissue of their head and neck muscles.
Several white-crowns do stay here in Pennsylvania throughout the winter at feeders and in open areas such as lawns, weedy fields, brushy places along fences and woodland edges at low elevations, especially in the southeast part of the commonwealth. However, seeing one on our mountaintop property was a special treat.
It came in two days after the seven-inch snowstorm, landing in our feeder area with a dark-eyed junco, one of two species it hangs out with in the winter. The following morning it returned with a couple congeners—the closely-related white-throated sparrow—Zonotrichia albicollis. In fact, researchers believe that the white-crown—Z. leucophrys—diverged from the white-throat 750,000 years ago and separated from its sister species, the western golden-crowned sparrow—Z. atricapilla—50,000 years before the present, but that all three sparrow species split from Harris’s sparrow Z. querla 1.2 million years ago.
I must confess that I had often mistrusted other feeder watchers who reported white-crowned sparrows, figuring they were mixing them up with male white-throats, because we almost always have abundant numbers of the latter in the winter. After all, the adult sparrows of both species have black and white striped heads, white wingbars on reddish-brown wings and dark-striped brown backs, but white-throats have a yellow spot above its grayish beak and a bright white throat, while a white-crown has a grayish breast and a pink bill. Furthermore, the immatures of both species have brown and white striped heads, but the bill colors remain the same as the matures, and the immature white-throats have streaked breasts while the white-crowns’ breasts are plain.
In the few days I had to observe the white-crown, it seemed to be the dominant species, chasing off the white-throats from the birdseed I had strewn on the back step.
White-crowned sparrows are known as the “white rats” of ornithology because they can easily be kept in captivity for study, particularly of birdsong. They are also widely distributed, abundant, and easy to see in the wild. In the western United States, four western subspecies have provided lots of opportunity for study, particularly Z.leucophrys pugetensis, Z.l.nuttalli, and Z.l.gambelii. While four of the five subspecies migrate, Z.l.nuttalli, which breeds along a narrow strip of the southern California coast to Santa Barbara, does not. Z.l.gambelii intergrades with our subspecies Z.l. leucophrys in northeastern Manitoba and is the Alaska, western United States Rocky Mountains and western Canadian subspecies. It, in turn, intergrades with Z.l.oriantha in broken populations also in western Canada and the western United States. Z.l. pugetensis breeds along the Pacific Coast to northwest California where it meets with Z.l.nuttalli.
All of this wouldn’t be particularly important except that most of the lauded scientific studies have been done on the western subspecies and that the behavior of these subspecies differs substantially from one another. Most galling of all, at least to those of us in the eastern United States, is that our subspecies Z.l.leucophry, from which all the others may have evolved, is the least studied.
Thank goodness Roland C. Clement, a vice president of the National Audubon Society back in the 1960s, traveled to Goose Bay, Labrador, to observe what he calls “a subarctic and alpine zone bird” on its nesting grounds. It is, he writes in Arthur Cleveland Bent’s Life Histories of North American Cardinals, Grosbeaks, Buntings, Towhees, Finches, Sparrows, and Allies, an “open, stunted tree growth and brush that attracts nesting white-crowned sparrows… I found them nesting only in the open, often burned, black spruce and dwarf birch on the high, sandy delta of the airport plateau [at Goose Bay].”
On June 16, 1957 he discovered a bird building a nest, forming a cup in a bed of hairy-cap mosses and Cladonia lichens, weaving it of grasses, lining it with fine root fibers and tucking it beneath a dwarf birch. Of the 30 nests he found in Goose Bay, all were built on the ground, but other researchers on the Labrador coast located them in small firs. These nests — four inches in diameter and two and five-eighths inside — are the smallest nests of any of the subspecies.
Two weeks later, Clement was in Quebec and found a nest with eight eggs and three parent birds, two females and a male, proving that at least a few of these birds engage in polygyny. In addition, he observed that a single female lays three to five eggs (the other subspecies lay as many as seven) and incubates them from 11 to 16 days. The young develop quickly and can fledge as early as nine days if they are disturbed to as long as 12 days, although the average is ten days. Both parents attend to nest sanitation and feeding the nestlings. To encourage them to fledge, the parents stop feeding them. Seven to ten days after they leave their nest, they can fly.
White-crowns are principally plant eaters — 92% of their diet — but they also eat insects especially from April until August when, presumably, they need more proteins to sustain themselves and their young. Mostly, they consume a wide variety of weed seeds (74%), with smaller amounts of berries and small grains. Clement observed up in their breeding grounds that they eat the green capsules of hairy-cap moss and furthermore, that he watched one white-crown pick and eat 120 capsules in one minute.
Like the white-throat, white-crown males sing all year, although they are particularly active in the spring, especially when they are busy acquiring their territory and mating. Clement says he counted 194 consecutive songs from one white-crown. They use their songs to defend their acre or more territory, attract a mate, and stimulate their mate’s reproductive capabilities. In addition, they can use the songs of other white-crowns to distinguish between neighbors and strangers, different dialects and even different subspecies. The eastern white-crowned sparrow song does show fewer small-scale differences in song dialects among populations than those in the western subspecies which is probably why white-crown song study has all been done with western birds.
One recent study discovered that older white-crowns will ignore the singing of younger ones in their territory, but aggressively defend their territory from rivals their own age. Another study found that younger males have a harder time attracting females than older ones.
White-crowns have also been used in numerous studies of how birds learn songs. Recently, researchers discovered that young white-crowns don’t need to hear a song in its entirety to learn it correctly. Gary J. Rose of the University of Utah and his colleagues played the white-crown song to young white-crowns in two-part phases — BA and DC instead of AB and CD for example — and the youngsters were able to piece together the typical white-crown song in reverse. But without the pairing, the young birds sang a jumble. This early musical exposure, Rose says, influences combination-sensitive detectors in their brains, allowing them to piece together song elements of nearly normal length with melodies dependent on what paired snippets they heard.
When researchers aren’t studying them, young white-crowns listen to their fathers and learn perfect “Oh gee—it was the whiz-whiskey” or “more wet wetter chee zee” white-crowned sparrow song. To Clement, “sitting in my tent or in some miner’s shack in the iron ore belt of interior Labrador in 1957, the song of the white-crown reminded me of a diminutive eastern meadowlark.”
Inclement weather, particularly snow storms on their nesting grounds, causes the most mortality in white-crowns, but shrikes, snowy and short-eared owls, sharp-shinned hawks and American kestrels prey on them.
The eastern white-crowned sparrow has continued to extend its winter range both eastward and northward since 1950. Clement attributes it to “climatic amelioration,” the planting of multiflora rose, which provides great cover in the open areas they favor, and the huge increase in bird feeding. They also relish the seeds of plants we scorn—pigweeds, foxtail-grasses, panic grasses, smartweeds, chickweeds, docks and ragweeds.
Once they weathered last October’s snowstorm, the living must have been easy for those that chose to spend the mildest winter in living memory here in Pennsylvania.