Fun Facts About Winter Nutrition
Bird feeders can be an important food source during winter. When severe weather impacts wild food supplies, some species of birds will turn to feeders as a critical food resource. It is during these times that feeders play their most vital role. If a storm is of long duration or extreme impact, a feeding station may mean the difference between life and death for these birds.
There is no evidence that birds using feeders will alter their seasonal feeding habits when switching between seeds, insects and fruit.
A Pygmy Nuthatch's diet switches from eating mostly insects and spiders in the summer to primarily eating seeds in the winter. It visits feeders where its favorite foods are sunflower seeds and suet.
Studies show that birds do not become dependent on bird feeders. Research studies on Black-capped Chickadees have shown that only 20-25% of its diet will come from using feeders, the rest still comes from natural sources...even in winter. It is reasonable to conclude this is true of other feeder birds and that 80% of their diet is still from the natural sources.
Birds usually eat a quantity of food necessary to satisfy their energy needs, their food intake fluctuates with environmental temperature, their activity level, and the energy concentration of the diet.
If a bird decreases its intake of food due to lower energy needs, its dietary need for other nutrients increase proportionally. Conversely, if food intake increases, the required concentration of nutrients decreases proportionally.
Have you noticed how ravenously the birds eat at your bird feeders, especially first thing in the morning and just before dusk? They are stoking their internal heater to get the day started and replenish fat reserves for another cold night.
The average bird in an average environment must forage about five hours per day to meet its energy requirements. In winter, they may have to forage longer for much-needed energy.
During cold weather chickadees have been found to need twenty times more food than they do in summer.
When the temperature falls below 10º F (-12ºC), chickadees with access to feeders have a higher winter survival rate of 69% versus a 37% survival rate for populations without access to feeders.
Lipids are the most concentrated energy source that a bird can consume.
Lipids are substances such as a fat (like suet), oil (found in seeds) or wax (usually from tree fruits).
Dietary lipids supply energy and are the only dietary component that is deposited intact into tissue.
Storage pools of lipids (fats reserves) are the primary energy supply that fuels a bird between meals, through cool winter nights and throughout migration.
Songbirds and other small passerines may use up to ¾ of their fat reserves in one night then replenish those fat reserves the next day. As with chickadees this can be as much as 10% of their body weight.
Species with unreliable winter food sources store more fat than species with a more predictable food supply.
When fat reserves are depleted, protein, mostly from muscles, is depleted to sustain energy needs. So it is important for birds to eat plenty of calories each day.
A bird expends 60% of its energy through body heat.
Small birds conserve energy overnight by decreasing their body temperature. It is called "controlled hypothermia" when their temperature is between 25-35˚C (77-95˚F). It is considered "torpor" when their body temperature is below 25˚C (77˚F).
Chickadees are able to perform a controlled hypothermia at night to drop their body temperature about 12 to 15°F (-11º to -9ºC) lower than their normal day-time temperature. This allows them to conserve about 25% of their energy every hour at freezing temperatures.
The Pygmy Nuthatch is the only songbird that uses three different survival techniques simultaneously in order to endure cold winter nights. It roosts inside a protected tree cavity where it huddles together in a communal group with other nuthatches and it conserves energy by lowering its metabolism and body temperature.
Pygmy Nuthatches have never been observed to roost alone. They will always roost at night in a communal group which may contain up to 100 birds. This tightly packed mass of birds can warm the roosting cavity by 40° F or more over the outside temperature.
Chickadees have excellent coping tactics for surviving harsh winter weather. They cache foods and remember where they are hidden, have dense winter coats, diligently find excellent, well-insulated roosting cavities and can perform a regulated hypothermia to conserve energy overnight.
As opposed to fats, carbohydrates are an essential form of energy for juncos, sparrows and other ground-feeding birds. They prefer to eat quantity over quality being able to pull useful energy and the nutrients they need from carbohydrates. They gobble up large quantities of high-carb foods and sit in protective cover and digest.
The top recommended carbohydrate food for ground-feeding birds is primarily millet. Recommended blends include Select and No-Mess.
The top recommended (lipid) foods for birds to meet energy cravings are:
Recommended Blends: Choice, No-Mess HC (high chips), Supreme, BugBerry Blend, Nutty for Nuts
Recommended Seeds: Peanuts, Nyjer, Sunflower Chips
Recommended Other Foods: Stackable Seed and Suet Cylinders, all of Jim's Birdacious Treats