The house sparrow is one of the most famous and widespread birds in the world, belonging to the passerine family. These small birds are striking in their resilience. They lead a sedentary lifestyle and rarely migrate to warmer climes, which makes their survival in harsh winter conditions a real master class in adaptation.
However, it is important to note that despite their general hardiness, in some regions of Western Europe, sparrows are experiencing significant population declines, indicating the vulnerability of even the most adapted species to rapid changes in the urban environment.
The search for a better fate
The rare sparrow migrates over long distances, the vast majority of these birds remain within their usual range, which usually does not exceed 3-5 km from their place of birth. However, closer to winter, their behavior changes: they begin to make the so-called “nomadism” – short movements in search of more favorable conditions. Some individuals may move a little further south within their region, but the most common tactic is to move closer to human settlements.
This choice is not accidental. Human settlements create the so-called “urban heat island effect”, where temperatures can be 2-5°C higher than in the surrounding rural areas. Even such a small increase in temperature significantly increases the sparrow's chances of survival, as it reduces the energy expenditure to maintain body temperature. Moreover, it is easier to find food and shelter from predators and the weather near homes.
Hidden neighbor
Unlike many other birds, sparrows often choose unconventional places for wintering. They can be found near transformer boxes, on electric wires or near heating mains. This is their strategic choice: by choosing a person as a neighbor, the sparrow provides itself with a warm rear. While we are warming ourselves in our homes, birds settle in sheds, attics, cracks in walls or ventilation holes. These places provide not only warmth, but also protection from wind, snow and predators.
Sparrows don't need humans to know they're there. They're adept at using our resources, from hauling seeds from a sack in a barn to picking up crumbs from a dog bowl. Their ability to find food is key to survival.
Winter menu change
In the summer, the sparrow's diet is very diverse: it includes seeds, berries, and a variety of insects, which are an important source of protein. However, in the winter, when insects are practically absent, nature makes a choice in favor of the sparrow, offering it mainly vegetarian dishes. This transition requires the birds to adapt and search for high-calorie plant foods.
During this period, a person becomes a kind of “good waiter”. Seeing how birds are looking for food, we can help them. It is best to give unroasted and unsalted sunflower seeds, millet, crushed corn. Bread, especially fresh, should not be given, as well as any salty, fried or spoiled foods, as they can be harmful or even deadly to birds.
Reproduction issues and parasites
Although the active nesting period in sparrows falls on spring and summer (from March to August, with 2-4 broods), the first signs of mating behavior can be observed much earlier. As early as early December, young birds can begin searching for partners, and in late February, formed pairs resume interaction and “flirting”. This is part of their reproductive strategy, which allows them to maximize the number of broods.
Sparrows are prolific breeders, with chicks being born 2-3 or even 4 times a year. The young quickly become independent. After the chicks leave the nest, the parents can begin repairing the worn-out nest for the next brood or look for a new location. However, towards the end of August, sparrows usually stop spending the night in their nesting boxes.
This behavior is important for combating parasites (mites, fleas, lice) that accumulate in the nest during the breeding season. By leaving the nest, the birds interrupt the life cycle of the parasites, and their population decreases. Closer to October, sparrows begin to actively collect small building material: feathers, plant fibers, pieces of plastic, threads – anything that can be used to patch up the cracks in their winter shelters. These are not always old nests, they often equip new, well-insulated collective perches in buildings, under roofs or in dense thickets to protect themselves from the cold.
The “balloon” principle
A winter sparrow, fluffed up like a feathered ball, is not at all like a summer bully. In the cold, sparrows specially fluff out their feathers. They do this not to seem bigger or stronger, but with one purpose – to increase the volume of the air cushion between the body and the external environment. Air is an excellent insulator, that is, a poor conductor of heat.
Thanks to this layer of air trapped between the down and contour feathers, the energy stored by the body “evaporates” more slowly. This is similar to the principle of layered clothing in humans. When a bird is cold, it instinctively fluffs its feathers, increasing the number of air chambers and effectively warming itself. This behavior is vital for minimizing heat loss and conserving precious energy, which is worth its weight in gold in winter.
Collective survival
Although sparrows may seem quite tenacious (e.g., fighting for a piece of bread), in winter they show amazing sociality, gathering in small colonies or flocks. In summer, when food is plentiful, grouping also occurs, but not always. In winter, when every grain is worth its weight in gold, collective interaction becomes a key factor in survival.
It happens that the one who has discovered provisions will definitely call his relatives to the meal with characteristic sounds. This mechanism is embedded in genetics and is a form of “mutual assistance” that is necessary for the survival of the entire population.
In addition to foraging together, grouping provides other benefits: social thermoregulation (birds huddle together, reducing the surface area of contact with cold air and preserving heat) and reducing the risk of predation (the more eyes, the easier it is to spot a predator, and each individual bird has a lower chance of becoming a victim).
“Dance” on one leg
To keep warm, sparrows use not only their feathers, but also their own limbs. You can see them standing on one leg, while hiding the other in their plumage. This is not just balancing, it is an important thermoregulation mechanism. Their tail, proportional to their body, helps maintain balance while they warm one limb and then change it.
The key physiological process here is countercurrent heat exchange. The blood vessels in the sparrow's legs are arranged in such a way that warm arterial blood flowing from the body to the foot passes next to cold venous blood returning from the foot. Heat is transferred from the arterial blood to the venous blood, causing the hot blood to cool before reaching the tips of the feet, and the cold blood returning to the body to warm. This minimizes heat loss through exposed areas of the body, allowing the feet to remain significantly cooler than body temperature without freezing, while maintaining normal blood circulation.
