Ecology of Birds in Winter

Life in Ontario is dominated by seasonal changes in climate, punctuated by winter. The majority of bird species that breed in eastern Ontario migrate out of the region to avoid the winter conditions, but a few species remain, and others still come to the region, typically from the north. Many of these wintering species show remarkable adaptations to their cold, dark and snow-covered environment.

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The goal of this course is to explore the ecology of birds in winter, examining adaptations of various species to surviving under difficult conditions. We will consider factors that limit the geographic distributions of species, particularly at northern latitudes, how species partition habitat and food resources, mixed-species flocking, the importance of food caching, large mammal kills, and roost sites, patterns of movement through the winter, and morphological and physiological adaptations to winter conditions. We will also consider the impacts of global climate change on the wintering distributions and ecology of local species.

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Students will learn skills of field identification of birds, recording natural history observations, designing and conducting field studies, and analysis and presentation of results. The field course will focus on the immediate area of the Queen's University Biological Station, but will include day trips to nearby open water and congregations of birds (Wolfe or Amherst Island) and possibly boreal forest (Algonquin Park, depending on weather).

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Expect, and come prepared for, extremely cold conditions and deep snow. Hiking in these conditions can be extremely difficult – students should be confident that they are in good physical condition.

Major Presentations     

Boreal Bird Population Irruptions

Many boreal birds, including birds that eat seed, fruit, small mammals, and mid-sized mammals, show dramatic winter irruptions southward. These irruptions are periodic and illustrate important dynamics of winter ecology of high latitude birds. Review evidence for boreal bird irruptions and the causes and consequences of irrupting bird populations.

Cold and Thermoregulation in Birds 

Birds are endothermic organisms, maintaining high body temperatures even in the face of cold environmental temperatures in winter. These cold environmental temperatures set important limitations on energy balance for birds. Review the diverse adaptations that have evolved to deal with living on the energetic edge in winter.

Northern Distribution Limits of Wintering Birds and Climate Change  

Recent changes in climate have already had dramatic influences on the wintering distributions of some birds in the northern hemisphere. Review the evidence and possible mechanisms behind these recent shifts in winter distributions. What can we expect for the future, both in terms of shifts in distributions and changes in winter bird species diversity? Why do some species of bird shift their distributions, while others do not?

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Fruit as a Food Source for Wintering Birds 

In contrast to seeds, many fruits are designed by the plant to be eaten by birds. Frugivorous birds in turn provide a service to the plant, dispersing their seeds. Review winter frugivory in birds. What adaptations do frugivores have for eating fruit? What plants fruit in the wintertime in eastern Ontario? How do fruit-bird interactions determine the distributions and movements of birds in winter?

The Importance of Large Mammal Mortality for Wintering Birds 

Winter is an energetically difficult time for many organisms, including large mammals. Starvation and predation lead to winter mortality in White-tailed Deer (locally) and Moose (Algonquin), creating carcasses that are a critical resource for a surprising array of birds. Review evidence for the importance of large mammal carcasses for wintering birds, and discuss the interactions between large mammal predators, their prey, and scavenging birds.

Caching Food for the Long Winter 

Food is a limiting resource for many species in winter, when primary productivity is low and snow and ice covers many food sources. Several species of birds solve the problem of low food availability by storing food for the winter. Review evidence for this behaviour in our local wintering birds (include boreal species if you wish), and discuss adaptations to caching, and the costs and benefits of taking such a strategy.

Mixed-Species Associations of Birds 

Many species of bird, fish, and mammal move or congregate in groups with other species. These mixed-species assemblages are common in wintering birds in eastern Ontario, and may provide important advantages. Discuss the reasons why wintering birds may associate in mixed-species flocks, and evidence to support these ideas. What are the costs and benefits of mixed-species flocking in winter? How can we differentiate between species that are attracted to each other (e.g., mixed-species flocks) and species that simply come together to use a limiting resource (e.g., multiple species feeding on a mammal carcass or at a bird feeder)?

Winter Storm Events and Ecological Adaptations of Birds for Survival 

Winter storm events, including blizzards and freezing rain, can result in high mortality for some birds. Why are winter storm events a problem for wintering birds in our region, and how have birds evolved strategies to deal with these events? What characteristics of winter storms are most difficult for birds to endure?

Roost Site Selection in Wintering Birds 

Long winter nights can challenge the energetic limits of birds, particularly just before morning when temperatures are often the coldest. To compensate for these challenges, many winter birds select their roost sites carefully, and may alter their roosting behaviour depending on weather conditions. Review the diverse strategies used by roosting birds in winter, and discuss the benefits of different roost sites and strategies. Is competition for roost sites important? Do competitive interactions give way to mutualistic associations when temperatures become cold?

Adaptations of Predatory Birds to Winter 

Predatory birds feeding on vertebrate prey encounter difficult conditions in winter. Prey populations rise and fall with time, move across the continent, and can become, at times, remarkably scarce. Worse still, snow conceals some prey, while other prey use a diverse array of adaptations to avoid their predators. Review adaptations of predatory birds that feed on vertebrate prey in winter. Be sure to include the families Accipitridae (hawks and eagles), Falconidae (falcons), Strigidae (owls) and Laniidae (shrikes). In your opinion, what adaptations are essential to survival of predators in winter?