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Snow Bunting
Plectrophenax nivalis
Order
PASSERIFORMES
– Family
CALCARIDAE
Authors: Lyon, Bruce, and Robert Montgomerie
Revisors: Montgomerie, Robert, and Bruce Lyon

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Introduction

Breeding male Snow Bunting, Prudhoe Bay, AK, June.
Figure 1. Distribution of the Snow Bunting in N. America

The arrival and song of the male Snow Bunting herald the end of the long, cold, dark winter in high arctic regions worldwide. Males return to their high arctic breeding grounds in early April, when the temperature can dip as low as -30°C and food resources are largely snow covered. Such early arrival can thus be energetically costly, and unseasonable storms can occasionally be devastating for early migrants. Females arrive four to six weeks later, when days are warming and snow is beginning to melt.

Why do male Snow Buntings return to the tundra so early in spring?  Unlike most other arctic songbirds, this species nests in rock cavities, so competition for territories containing high-quality nest sites is intense. The importance of nest sites to the reproductive biology of Snow Buntings is underscored by the fact that nest-site advertisement and visitation are a key part of courtship. By tucking their nests deep in narrow cracks and fissures, Snow Buntings suffer lower rates of nest predation than open-nesting arctic songbirds. This safety, however, comes at a cost—cold rock cavities have a harsh microclimate for developing eggs, one that can increase incubation periods or kill developing embryos. To ameliorate this cost, male Snow Buntings feed their mates on the nest throughout incubation, an indirect form of parental care that allows females to spend more time on their nests and, as a result, achieve a shorter incubation period and a higher hatching success.

Snow Buntings been studied relatively little in North America, owing to their remote breeding range in the high arctic, and their nomadic habits during winter. Our own work during the breeding seasons from 1980-1993—mainly at Sarcpa Lake (68°33'N 83°19'W), Melville Peninsula, Nunavut (NT)—provided much of the unpublished data in this species account, with additional information from our research on Jenny Lind Island, NT, in 1984 (BL); at Hall Beach, Igloolik, and Iqaluit, NT, in 1980-1995 (RM); and at Deadhorse (in 1993) and Attu (in 1994), AK (RM). John Wingfield and collaborators have also studied this species extensively during the breeding season at Barrow, AK (71°15’N, 148° 45’W) in 1994-2002, focusing on reproductive physiology. As a result of all this work, and Tinbergen’s (1932) monograph, we know quite a bit about the basic breeding biology of this species, but there is tremendous scope for further interesting research with respect to parental care and territoriality, using modern field study methods including nest monitoring, radio-telemetry, and paternity analysis.

Recently there has emerged some evidence that this species is in serious decline in North America, being listed, for example, as one of 20 species whose population size has decreased by more than 50% during the past 4 decades, based on Christmas Bird Counts (CBCs). If this is a real decline (CBC data may not census this species accurately), the reasons for it are far from obvious, and deserve intensive research, particularly focused on monitoring both breeding populations and annual productivity across the breeding range. For example, this apparent change in population size may be due to shifts in winter distribution, possibly resulting from climate change, and not to any overall population decline. Research is urgently needed to document current population sizes and reasons for any recent changes.