Photo Credit: Ken Otter
The Cheeky Chickadee
On a winter walk through town or down a country road, you will probably be greeted by the unmistakable call of the chickadee: Fee-bee. Fee-bee. Chick-a-dee-dee-dee.
These energetic little birds are winter residents in the North and, though they are common, they are anything but ordinary. Tough, resourceful and perfectly adapted to cold environments, they are highly evolved survivalists.
Four chickadee species are found in northern BC: black-capped, mountain, chestnut-backed and boreal. The black-capped chickadee is by far the most common and is often seen at backyard birdfeeders. They are easily identified by their black cap and grey backs and are found in open mixed forests with plenty of deciduous trees.
The mountain chickadee looks similar to a black-capped, but has a white stripe above the eye. Mountain chickadees prefer coniferous forests and are common in the drier interior and at slightly higher elevations. Black-capped and mountain chickadees are in the black-headed clade, or group.
The brown-headed clade includes the chestnut-backed chickadee and the boreal chickadee. Chestnut-backed chickadees are common on the coast or in wetter forests and are easily identified by their rich, rusty brown-coloured backs and sides and a lighter cap. Boreal chickadees are shyer and have a brown cap and brownish back and sides with much less white on their cheeks. As their name suggests, they are found all through the boreal forest.
Survival of the thickest
Each of these chickadees has a slightly different ecological niche; however, their survival strategies are very similar. Ken Otter, biology professor at the University of Northern British Columbia, studies many aspects of chickadee behaviour: “Chickadees are winter survivors,” Otter says. “One physiological adaptation they have made to survive cold temperatures is nocturnal hypothermia. At night chickadees will drop their body temperature from 40 C to 30 or 32 C, which helps them conserve energy.
“It is a pretty amazing feat. They fluff up their feathers, which are very dense and thick. This traps a layer of warm air next to their body, like wearing a fluffy down jacket. Their feet get cold because they are putting them on cold branches, so they pull their feet up and tuck them against their skin, kind of like sticking your hands in your armpits to warm them up.”
In this state, their respiration and heart rate drop, and they enter a state of unconsciousness called torpor. Another strategy is to build up an additional layer of fat during the day and burn it overnight.
“A chickadee will gain 10 percent of its own weight every day,” Otter says, meaning the 11-gram birds gain and burn about one gram daily. “They have an incredibly fast metabolism. They never stop moving when you put them in a cage and are bouncing all over the place. They are very hyperactive.”
This hyperactivity can be easily observed during the day, as chickadees are almost constantly in motion. Another way they keep warm is shivering thermogenesis, which is a shivering behaviour that produces heat. The shivering motion isn’t visible, but it helps keep their bodies at a stable temperature when sitting still on a branch; even sitting still they are moving. This behaviour demands more energy, which is supplied by a high-calorie diet.
To keep up with these energy demands, chickadees have to eat constantly, taking advantage of food when it is abundant by stashing it away for leaner times. Otter explains, “Chickadees are scatter hoarders, which means they put food in different locations. They have a section of their brain called the hippocampus, which is associated with spatial memory. That part of their brain actually grows during the winter, the time when there is more cellular activity and generation.”
A chickadee may store as many as 100,000 food items per year, scattered throughout its territory.
“A research team in Reno has done a lot of work on this. If you compare within a species (black-capped chickadees) between different populations (Alaska and Nevada), their caching abilities are better in relation to how cold the winters are. This difference can even be seen between lower and higher elevation—birds living in areas with shorter summers and longer winters have more developed spatial memories than birds in milder climates,” Otter says.
In addition to thermoregulation and feeding strategies, chickadees have defence systems that help them survive.
“Black-caps will group together and use each other for food finding and food defence. If they find food, they will call and bring more of their flock to them.” While sharing seems like a counterintuitive survival strategy, Otter explains how it benefits the individual: “Sharing with your flock mates will benefit you because then you can defend the food source as a group.”
If another bird comes to the food source, the chickadees will harass the interloper by dive-bombing it constantly. Chickadees use similar tactics to defend themselves against predators.
“The success of an owl or hawk making a kill is significantly less when they are being harassed, so they eventually leave,” Otter says. This dive-bombing and harassment tactic is called mobbing. Chickadees also use their distinctive call to attract other birds to join in defence during threatening situations.
“When the chickadees find the predators, they will give a fairly accurate representation of how distressed or motivated they are by the number of dee notes in the chick-a-dee-dee call. The more the predator is a threat, like a small owl or hawk, the more dee notes they give when they are mobbing it. If it is a great grey owl—a predator that is less likely to prey on chickadees—fewer ‘dee’ notes are called.”
Humans can help chickadees make it through the coldest part of winter by providing food, shelter and even water. Backyard birdfeeders provide extra calories for the hungry birds. The all-black oil sunflower seed is higher in fat than the striped variety and easier to crack. High-fat foods like suet are also beneficial. Feeders should be placed in a sheltered spot, out of the wind and near cover such as trees or bushes. Providing water in a heated container reduces the energy-consuming need for chickadees to melt snow for water. Chickadees roost individually in small spaces for cold winter nights, so providing small, cozy roost boxes can help increase survival. A roost box is different from a nesting box in that it is insulated and the entrance hole is at the bottom so less heat escapes.
As winter sets in and feathered visitors start dashing back and forth from your feeder, take a minute to watch where the chickadees are hiding food. Watch them mob an unwelcome visitor and listen for their alarm calls. Rather than thinking of chickadees as small, plain and plentiful, imagine them as the truly marvellous survivors that they are, and pay them the respect they are due.