Snow Buntings Pay an Energetic Price for Wintering Nearer Their Breeding Grounds
Study shows Arctic songbirds face higher metabolic costs when enduring harsher northern winters in exchange for shorter spring migrations
Balancing benefits and costs
A new study in Ornithology has revealed the physiological trade-offs faced by Snow Buntings Plectrophenax nivalis choosing to winter closer to their Arctic breeding grounds. While remaining further north in Canada offers the advantage of a shorter return journey in spring, the research shows that these buntings must endure substantially higher energetic costs to survive long, frigid winters.
“Snow Buntings wintering in northern latitudes were heavier, carried larger fat reserves, and had greater lean tissue mass compared to those wintering further south,” write Marianne Turcotte and colleagues. These adjustments allow the birds to endure severe cold but come at the expense of a higher basal metabolic rate (BMR), meaning they burn more energy simply to maintain body functions during winter.
Measuring the price of cold
The research team compared buntings captured across southern Ontario and Québec with those from the harsher northeast near the Gulf of St. Lawrence. Despite no differences in skeletal size, northern birds were on average 8% heavier, carrying 32% more lipid reserves and 4% more lean tissue. They also had slightly thicker breast muscles - critical both for flight and for generating heat through shivering.
Metabolic measurements confirmed the extra cost: northern birds had a 6–8% higher BMR, even after accounting for their additional muscle mass. In other words, not only were they carrying more metabolically active tissue, but that tissue itself was working harder to cope with cold exposure.
Why winter further north?
For many migratory birds, wintering nearer the breeding grounds can provide a crucial advantage. Male Snow Buntings often return to the Arctic earlier than females, securing prime breeding territories. A shorter spring migration from northeastern wintering grounds could therefore improve reproductive success.
But this strategy carries risks. Harsh winters mean unpredictable food availability, shorter daylight hours for foraging, and prolonged cold nights. The study shows that buntings respond by stockpiling lipids - their key winter fuel - and by enlarging flight and internal organs to process more food. This helps them endure the cold but locks them into an energetically expensive way of life.
Implications for changing winters
Snow Buntings are declining across much of their range, and understanding the physiological pressures they face is key to conservation. The authors caution that climate variability may complicate this trade-off: milder winters could reduce metabolic costs in the north, but less predictable snow cover could alter food availability. Conversely, harsher winters might push more individuals south, lengthening their migration and potentially delaying breeding.
“Our study illustrates the measurable physiological costs birds must pay to winter closer to their breeding sites,” the team conclude. “It highlights how migratory strategies are shaped by the fine balance between ecological opportunity and energetic constraint.”
August 2025
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