Snow Buntings

A flurry of wingbeats caught my peripheral vision as I was lowering my binoculars from scanning the Bay. The flock settled behind nearby ledges, at the edge of the moors, an odd place for the Purple Sandpipers that forage at the tide line. Nevertheless I folded the camera tripod legs and clambered over the rocks for a look. The birds took off down the coastline in a purposeful but jumbled group showing nothing like the tactical precision of sandpipers. They disappeared around the bend toward the grout pile.  Besides their bobbing, finchy flight they flashed remarkable white patches under wings. Kay and I packed off in pursuit.

Snow Buntings were on my short list of winter delights at Halibut Point. In seven years of exploration I hadn't seen one yet. Sibley's Field Guide to Birds offers the tantalizing note that they can be "common but irregular" in the northern states on open ground such as beaches and fields, foraging for seeds. After hastening along the shoreline we went up toward the grassy areas by the quarry. Park Supervisor Mark Peterson told us he'd just gotten a picture with his cell phone of what he was pretty sure were Snow Buntings. They've been scurrying around the Visitors Center parking lot for a couple of days. I had the classic twin reactions, "You're kidding!" and "Of course!"

A good look at Snow Buntings shows the tufts of feathers that help keep their legs warm, similarly to Snowy Owls. Both these species spend most of the year in tundra latitudes. The Buntings are usually back there by March, when much of the breeding male's plumage turns white to match its surroundings. To the extent that feather patterns govern sex appeal, I think we have the better pleasure with these off-season highlights of cinnamon and chestnut. 

The fact that their migration to the Arctic is entirely nocturnal has intrigued research biologists to study the Snow Bunting's navigational  systems. We may not know exactly how, but it's clear they find their way home by orienting to the geomagnetic energy fields of the earth and to celestial cues in the sky. This summary of experimental results adds to the curious allure of both nature and science. 

Orientation tests were conducted with snow buntings (Plectrophenax nivalis) exposed to artificially manipulated magnetic fields, during both spring and autumn migration. Experiments were run under clear sunset skies and under simulated complete overcast. The birds closely followed experimental shifts of the magnetic fields during both seasons regardless of whether they had access to celestial cues. Clear-sky tests in vertical magnetic fields resulted in a significant bimodal orientation, the directionality of which was almost identical during spring and autumn. When the snow buntings were deprived of celestial directional information and tested in vertical magnetic fields, they failed to show any statistically significant mean directions in either spring or autumn. The results demonstrate that snow buntings possess a magnetic compass and suggest that magnetic cues are of primary importance for their migratory orientation while on passage through temperate-zone areas. However, the axial orientation in vertical magnetic fields under clear skies may indicate an involvement of celestial cues as an auxiliary source of directional information. 

R. Sandberg and J. Pettersson, "Magnetic orientation of snow buntings (Plectrophenax nivalis), a species breeding in the high Arctic: passage migration through temperate-zone areas," Journal of Experimental Biology vol. 199 no. 9, 1996.