How wintering birds use people

It is well known that on the ground only a strip near the equator is characterized by the lack of seasonal changes in the climate and weather. The farther from the equator, the more seasonal differences in the external living conditions of animals and plants. Annual rhythm is especially pronounced in birds inhabiting moderate and polar zones. Due to the brevity of the favorable period in high latitudes, the duration of the nesting season is reduced. At the same time, its amplitude increases, that is, a larger number of individuals are involved in reproduction at the same time.

In addition, with an increase in geographical latitude, the average daily air temperature decreases. Therefore, birds, propagating and growing in the northern latitudes, experience additional energy loads associated with the need to maintain their own existence, multiply and grow at temperatures below the boundary of the temperature optimum.

Bird migration is one of the forms of adaptation to the seasonality of climate, which allows birds to have a large number than with a settled lifestyle. They also make it possible to use the territory, favorable in one season and unfavorable in other seasons.

Repeatedly proven that from the point of view of migration, all bird populations behave very differently. Within each population, birds are born that do not migrate at all. There are those in which the migration state is expressed to varying degrees. There are birds with a hypertrophied migration state. Thus, natural selection always has sufficient source material to change the reaction rate in the population both in the direction of sedimentary and in the direction of flights. If necessary, the terms, range and direction of migration may change.

If the birds migrate, then this does not require a change in the fundamental feature of their existence - the total amount of energy that they can absorb from the environment. Migrations only change the annual energy consumption cycle, reducing the needs in winter and raising them in the spring, summer and autumn, that is, in more favorable seasoning for food.

On the contrary, in sedentary birds of moderate and high latitudes, maintaining a favorable energy balance in the winter requires a decrease in heat transfer and an increase in the ability to absorb a larger amount of food. Life in difficult conditions requires the restructuring of many fundamental systems in the body, both physiological and morphological.

The development of adaptation to cold conflicts with the need to maintain resistance to high temperatures in the summer. This contradiction is solved by a seasonal change in thermal conductivity, heat production and the maximum level of food consumption. In addition, adaptation to a sedentary lifestyle in high and moderate latitudes requires the development of the ability to change the nutrition, and winter food often turns out to be either difficult to digest, or low -calorie, or, finally, difficult to work. It is possible only after developing deep adaptation at the morphological and physiological levels.

A decrease in temperature to minus values ​​and snow loss are the most adverse factors of winter. Water and soil freeze, plant vegetation ceases; Most of the insects, mollusks, worms, amphibians, reptiles and part of mammals flow into anbiosis, hibernation or hide. Therefore, birds lose many available habitats.

In the absence of snow cover, even when soil freezing, birds that feed on plant seeds can collect those seeds that remain on the plants themselves, and those that were scattered on the basis. In the same way, insectivorous birds can look for insects hidden in the grass and soil. However, even a slight snow cover leads the birds to the need to break snow, and deep snow makes all the food inaccessible. And then people come to the rescue.

Man has long become one of the most important components of the ecosystem, and in winter in temperate latitudes wintering birds often count on it. Thanks to people, the influence of basic unfavorable factors is reduced. In winter, especially where the number of people is great, wintering birds prefer to concentrate around and within human settlements.

People, their dwellings, their production facilities, etc. create a huge amount of additional heat, which leads to both global and local temperature in cities. The dwellings of people and their production facilities provide a huge number of warm niches and shelters, where wintering birds can leave and warm up. An increase in temperature near human dwellings and special purification by people of certain territories from snow reduces the spread and depth of snow cover.

In addition, a person produces, stores, processes and throws a huge amount of food. Naturally, birds use this resource and concentrate around such places, eating food and/or other animals that also use it. So a person, often not wanting it himself, contributes to the successful wintering of many birds. And the concentration of birds around human settlements is a behavioral adaptation that increases the survival of wintering birds.

At the same time, recently, a directed role of a person in an increase in the survival of wintering birds has also increased. More and more people purposefully and constantly feed birds in the autumn-winter period. Two main directions of bird feeding are distinguished: directed top dressing of certain species and the creation of special feeders that visit different species of birds.

In the middle lane of Russia, wintering birds can be divided into five groups.

The first form species that are completely dependent on a person. These are city pigeons, sparrows and city ducks. These species outside the settlements of a person cannot exist at all; The amount of feed that they can find in nature is so small that it will not allow them to survive the winter.

The second group is formed by sedentary forest birds, regularly wintering in the middle lane and quite adapted to this.

These are tits, cuttings, woodpeckers, greenfinch, soyshops. They can survive the winter without the help of a person, but will not give up the latter. These birds willingly and feed a lot on the feeder. The third group is formed by bullfinches, chogles, oatmeal, chi and tapers. In winter, these grain poultry feed on various seeds. They occasionally visit the feeders with pleasure eating seeds, but due to the nomadic lifestyle, they rarely remain at the feeders for a long time.

The fourth group is formed by drifts, waxworms, cigarettes and kings. These species can often be seen near human housing, but they never visit feeders because of their specialization in nutrition.

The fifth group is formed by gray crows and magpies. These species are best adapted for habitat together with a person; As a rule, no one specifically feeds them, with the exception of usually individually identified individuals.

Vadim Gavrilov,
Ornithologist, cand. Biol. sciences, Art. scientific. sore. biological
Faculty of Moscow State University Lomonosov

The photographs made by the author of the article present the types of the second group, which in the autumn-winter period can be seen on the feeders.