In cold climates, there are fewer birds around during the winter, but these hardy species face a wide variety of dangerous threats. Birders who understand those threats can help all their winter birds – in the field and the backyard – survive a perilous season.
How Winter Threatens Birds
The winter season may seem peaceful and serene, but in the crystalline beauty of snowflakes and the joy of winter holidays lurk many threats to birds. While birds have different adaptations to help them survive the season, these winter threats to birds make that survival far less certain.
- Cold Temperatures: Rapidly dropping temperatures can sap birds of critical energy and body heat, and it is possible to small birds to freeze to death in a cold snap. While birds have many ways to keep warm, a sudden drop in temperatures can be deadly.
- Storms: Prolonged storms can bury birds' food supplies and keep them stranded in roosts rather than out foraging. Birds caught in flight during a storm can also become disoriented and may be more susceptible to collisions or flying far off course.
- Food Scarcity: Food sources are naturally harder to find during the winter, and additional competition can mean some birds go without. Less food makes birds more vulnerable to cold, disease and predators. During the winter, many birds change their diets to better utilize available resources, but those resources can quickly run out, particularly during a long winter.
- Frozen Water: Birds need water to drink year-round, and when all the familiar water sources are frozen, they are forced to melt snow and ice to drink. That takes great energy just at a time when food supplies are at their lowest. Frozen water can also threaten waterfowl that may mistake a frozen lake for open water and crash land, and birds can occasionally get frozen to slushy ice surfaces when the water refreezes.
- Shelter Loss: As deciduous trees shed their leaves, birds lose essential shelter that can help keep them warm in the coldest season. This increases competition for other roosting areas, such as coniferous trees or hollow trees and other cavities. To compensate, many smaller birds form communal roosts, often crowding several adult birds into one small area for a nighttime roost.
- Predators: Predators can become more aggressive in the winter when their typical prey is less available, and birds can be especially vulnerable because of shelter loss that makes them easier to see. This is one reason why many birds adopt more camouflaged plumage during the winter.
- Disease: When birds are roaming in mixed flocks and roosting communally, they are more subject to disease outbreaks. Entire flocks can succumb to avian illnesses, particularly if the birds are already weakened by excessive cold and lack of food and water.
- Winter Sports: Studies have shown that birds in habitats near winter sports resorts have higher stress levels than birds in more isolated areas. This can lead to more illness, poor breeding and other consequences that can endanger alpine birds.
- Outdoor Decorations: Outdoor decorations for winter holidays endanger birds by destroying roosting areas, disrupting bird feeding areas and creating tangle hazards. This is especially hazardous when the decorations are overly extensive or are left up for extended periods.
- Birders: Winter is the season of bird irruptions and vagrant sightings, and even well-meaning birders can threaten the birds they are excited to see by accidentally flushing the birds out of protective cover and drawing the attention of predators.
How You Can Help
With so many threats and hazards, bird mortality is high during this inhospitable season. Fortunately, birders can take many steps to help minimize winter threats to birds.
- Put up multiple bird roost boxes in your backyard to offer seasonal, secure shelter to small birds. A brush pile can be another great form of shelter that is easy to create and will be useful for small birds and ground-feeding species.
- Invest in a heated bird bath to provide a source of clean, unfrozen water for birds. Be sure the bath has perches on the edge for drinking birds, and keep the depth adequate to provide a good continuous water supply.
- Offer the best winter foods for birds, such as suet, black oil sunflower seed, nuts and other high-calorie sources of fat that can give birds plenty of energy. Birds will rely on these feeders all season long, particularly during storms, so be sure to refill them frequently.
- Opt for bird-friendly landscaping that includes plenty of evergreen trees and shrubs to provide winter shelter for birds. Many evergreen plants also include berries that will be a great source of winter food, but be sure to prune in the spring rather than the fall so birds can take advantage of the food during the lean season.
- Take steps to discourage feral cats and other backyard predators. Birds face plenty of predators all winter long, and minimizing additional hazards from predators is essential.
- Keep bird feeders clean and regularly clean the bird bath as well to minimize the risk of spreading diseases when birds may be at their weakest.
- If you participate in winter sports, obey resort boundaries and only use appropriately designated areas for skiing, sledding, tubing and snowboarding. This will minimize the disruption to surrounding habitats that may be home to sensitive bird species.
- Minimize any outdoor holiday decorations you use or opt for bird-friendly alternatives, such as decorating a Christmas tree for the birds to serve as a festive feeding station.
- Obey rare bird ethics whenever you spot an unusual winter visitor to prevent adding more stress to a bird that is already in unfamiliar surroundings.
With care, every birder can take steps to make winter a more bird-friendly season and minimize the hazards all winter birds face.
Photo – Winter Blue Jay © Tim