Birds of the Glebe

The familiar Black-capped Chickadee stays with us all winter – how does she survive? PHOTO: JEANETTE RIVE

Our favourite little bird

By Jeanette Rive

Which is the most recognizable little bird at our feeders and in our gardens? The cheerful little Black-capped Chickadee, of course. Non-migratory, we see them year-round, either in small flocks of six to 12 birds in winter or in pairs as the nesting season approaches. Other birds, such as nuthatches, juncos, kinglets and creepers, like to hang out with the flock, taking advantage of the chickadee’s ability to find food and offer protection against predators. Their familiar chickadee-dee-dee is recognized by other birds and depending on the number of dees, the call is used to alert others of lurking danger.

They are fascinating little birds with characteristics that are either unique to them and others in their family, such as the Titmouse, or are shared with some other bird species.

How do these little birds stay warm in winter? How do they get enough food (apart from an ongoing supply of their favourite food, sunflower seeds, in our feeders)? Why don’t their feet get cold?

On cold winter nights, the chickadee is one of the few birds that can enter a state of torpor. This is not quite hibernation; rather, it’s a lowering of body temperature by as much as 12°C from their normal temperature of about 42°C to conserve energy. The common swift and a few species of hummingbirds also have this ability, but our winters are just too cold for them and they are long gone by August or September. Unlike many birds who roost in flocks to stay warm, the chickadee likes to sleep alone, finding a little crevice in a tree or in dense shrubbery to shelter from the wind.

As for food, chickadees engage in “caching” – hiding food to be found later. When you see a chickadee repeatedly coming back to the feeder, it isn’t being greedy, it’s hoarding food, especially in late summer and early fall when food is plentiful. It’ll tuck a little morsel or seed under a piece of bark or in some lichen or in a little crevice – it may even come back later to move the food if it thinks it might have been seen hiding it! They may cache hundreds of items in a day and can retrieve them with astounding accuracy up to 28 days later, even remembering which hiding spot they have already emptied. How do they do this? Birds that hoard food, which include nuthatches, some woodpeckers and crows, have a physiological response in their brains when this memory needs to be engaged – their hippocampus, which plays a major role in memory and learning in all vertebrates, increases in size in autumn and winter and decreases in summer and spring. If only our memories were as good as theirs!

Bird feet can stay warm-ish and flexible because their foot temperature is regulated to stay around the freezing point by ensuring that a constant supply of warm blood is circulated to the extremities. The veins carrying the blood lie adjacent to one another so that the warm blood going to the feet also warms the cold blood returning to the body, recovering most of the lost heat, an efficient heat exchange system which gulls, ducks and other birds who spend time standing on ice also have.

Chickadees pair off in the fall, stay together in a flock during winter and then in spring, the flock disperses to breed. They nest in a tree, quite high up, perhaps in an old woodpecker hole. The female lines the nest with vegetation and animal hair. Six to eight eggs are laid – they are about the size of a slightly oblong dime, white but lightly speckled with reddish brown spots. After about two weeks of incubation, the chicks hatch and are fed by the female. Approximately another two weeks later, they fledge and, like other hole-nesting birds, are able to fly immediately and don’t need to practise hopping from one branch to another. Both parents feed the fledglings until they can forage for themselves.Their summer diet is mainly caterpillars, insects and spiders along with berries, which they forage for among the shrubbery and twigs.

When cleaning up your garden, do leave some vegetation – after all, you don’t want to inadvertently remove the chickadee’s hidden food!

Jeanette Rive is a Glebe bird enthusiast and long-time Glebe Report proofreader.

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