Why martins are called “birds of weather“?
Generally, at martins are a lot of informal, poetic names. They are called both “children of air“, and “experts of the sky“. But about it as - nibud another time. And today - about why all - they are considered as “birds of weather“.
The matter is that food supply of martins - so-called “air plankton“. The small insects lifted in air by the warm ascending atmospheric streams. And there are these midges or not them and if is, then how many - depends only on weather conditions. Here life of martins also depends (and it is very strong!) from weather which practically across all territory of their nesting is subject to serious fluctuations.
Even the arrival of these birds stretched on time can last, depending on weather conditions, from 18 to 27 days. In the Leningrad region, in the south of Finland and Karelia it occurs approximately in the second decade of May, being slightly displaced to earlier terms at warm weather, and at cold spring - being removed for the end of month. But when martins fly, on the wings they, as a rule, bring steady, warm weather. And there is no miracle here.
As experts speak, to places of gnezdoviya martins fly “on a cyclone back“. They need insects. So, good, sunny weather. Here also birds against wind to areas of a high pressure fly that lie far from the center of a cyclone, on its suburbs. Fly that on “back“ of a cyclone to bring us on the wings heat and expectation of close summer …
But to them have no time to relax and luxuriate in tender sunshine. Day - another have a rest, and it is time to start or construction of a new nest, or capital repairs of what was constructed last summer. Days eight married couple are occupied with exclusively construction works. And as they come to an end, so in a tray of a nest there are two - three, but everything is more often - two, small white small egg.
Also process of their incubation which, besides, depending on weather conditions can strongly drag on in time and borrow from 11 to 16 (according to other data to 20) days begins. Martins, unlike many other birds, do not feed the nasizhivayushchy partner therefore if suddenly there comes bad, rainy weather, both birds throw a laying and depart to be fed up there where the sun shines and the ascending warm air streams lift from the earth of small insects. Sometimes such “absences“ last the whole days. Or even slightly longer.
And what laying? Yes anything. Strizhiny eggs, it appears, possess amazing survivability. Even in egg, two days lain in a cold nest, the embryo does not perish. As soon as parents come back and start over again warming it the heat, it safely develops further. But it if bad weather stopped and from - for clouds looked out the sun. And if is not present? Here then - affairs are bad.
It is slightly easier for adult martins. As a result of long evolutionary process the nature allocated them with one unusual feature, some kind of protective mechanism. In spite of the fact that birds generally warm-blooded (gomotermny) animals, body temperature of martins very strongly depends on ambient temperature and at instability of the last can test considerable, and sometimes and very sharp fluctuations.
Therefore if bad weather continues, martins come back to the nest and, waiting for serene days, sit out in is mute. At the same time temperature of their body falls to twenty degrees. The bird freezes and stiffens in an immovability. Metabolic processes in its organism are slowed down, and it falls into something, very similar to hibernation of bears, badgers, groundhogs. In such state the martin, without special harm for the health can carry out day four. Of which it is, usually, quite enough to wait for arrival of heat and the sun. And together with them and returns of insects.
Here it is not necessary to wait only for such amount of heat which is necessary for a normal incubation of the laying which is in a nest from the hungry, frozen bird. Therefore if it is not enough clear, serene days, and rains all go and go, martins throw out egg from a nest, from a tray aside. At first one. But if bad weather continues, after the first the second follows. And sometimes and the third.
However, if serene days come back, in a nest the new laying appears. There is only no chance left to sit out it and to bring up baby birds at birds practically. Days go, and in August it is already necessary to depart. When to bring up if this process, depending on weather, takes martins from 33 (under the most favorable circumstances) up to 56 days? The summer is in our corner of the world rare when passes without rains and short-term cold snaps.
And again if weather spoils, martins leave in a nest not eggs any more - baby birds, and... depart. In so-called “weather migrations“. Somewhere there, where the sun and a stern - shines much. Sometimes for 50 - 70 km from a nest. And baby birds remain. In itself. One. Hungry and cold.
And “cold“ - practically in literal sense of this word. They, as well as adult individuals, freeze, and temperature of their body goes down to such level that it is practically compared to air temperature. Also the metabolism in a small little body is slowed down.
Baby birds can be in such state days 9 - 12. And - anything. Without some sad consequences. Another matter if the compelled starvation lasts bigger term. Here then in two weeks baby birds will lose a half of the weight and will die. And 9 - 12 days... Anything terrible. Will grow thin, of course, not without it. But then good weather, and with it and parents who at once will begin to bring in a beak of different nutritious midges will return. And baby birds will go to growth again. That at the end of July - the beginning of August to take off from a nest. And almost right there - to depart on the South. Independently, without what tiresome parental guardianship.
And adult birds will a little more stay in places of gnezdoviya, will have a rest is sensitive from affairs just, and only after that will set the same course, as young growth. On the South, on the South …
By the way, time of flying away of martins for wintering is corrected by weather too. By the general ornithological rule, northern individuals of one bird`s look depart on winter quarters before southern. All because cold weather to them already came. And in the south of even warmly. Where to hurry? It is possible and wait a moment with flying away.
At martins - all exactly the opposite. Than to the south, that a high probability of the fact that the summer will be warm and serene. And if zadozhdit, then absolutely for a while. Therefore it is required to the “southern“ martins of time for an incubation and feeding of baby birds less, than to their more northern neighbors. Here also the Swiss martins to places of wintering before the fly away it is southern - the Karelian relatives.
Depart … Far - it is far. For the equator. Further away. On the South of the African continent.
But in May of the next year they will surely return. Also will bring us on the wings heat, good weather and expectation of close summer. The martin is a “bird of weather“.