Migration step. This is how migratory species change

Migratory Pass and the mysteries of migration: the physical differences between migratory and sedentary birds and the evolutionary magic of the wild that travels millions of kilometers in flight every year to survive.

It is a constant that accompanies the life of birds that every year, if migratory, move from one place to another on the globe to find ideal conditions for their survival. However, those who believe that migration is an immutable phenomenon are mistaken. The habits of birds change conditioned by various factors: the annual climate to begin with, the contingent needs and genetics are elements that should not be underestimated. If the phenomenon of migration were precise and immutable, many words would not be wasted to explain it, it would not study it with so much attention and above all the hunters at each seasonal change would not insistently call their colleagues, residing further north, to know the flow of migration, waiting for it to reach them. On the other hand, there are years of good pace and sadly deserted years, and no matter how hard we try to fully understand the reasons, still the migration of birds is a phenomenon that is largely mysterious and magical.

Migration: why?
Birds move for one reason only: to multiply the possibility of surviving and reproducing exponentially. This possibility increases considerably if the animals choose to move season after season, opting for ecologically different places. It is a fact: the nesting places at a given moment become inadequate for the permanence of some species: the birds abandon them because they consider them inhospitable. The reason is simple, seasonal climate change has decreased the availability of food; with the cold that has come, the plants no longer produce the food necessary for the sustenance of the birds, many insects have died and many others are below the level of the snow.

The birds have only one thing left to do: find a more comfortable habitat. Nothing unusual so far. What science has not yet managed to understand is the reason that pushes migrants to return to their nesting sites. The conditions offered by the wintering places are in fact always potentially optimal, or at least sufficient for the survival of the species: availability of food, hours of light always maintain acceptable levels. Therefore, the reason that pushes them towards the return to the nesting places often and willingly rather distant is not explained.

Migration: how does the species evolve?
To know the evolution of migration, already that we have said it, it does not remain the same, it would be important to know the physiological, behavioral and morphological adaptations of the species. This is rather complicated given that within the same population it is possible to present different stages of evolution. In general, however, we can admit that birds that are forced to long and tiring migrations are more subject to evolutionary forms: specifically, mechanisms are created that regulate the departure and orientation of the flight, an accumulation of seasonal fat occurs, and in some cases the morphology of the animal changes. On the other hand, the body of the bird is important to change in such a way as to be able to cover long distances in the best possible way. For example, if you choose to compare a migrant with a resident bird, you will notice some interesting details:
• wings. They are longer pointed in the migratory;
• tail. It is generally shorter;
• coracoid bone and sternum. It is longer the longer the distances covered by the bird are;
• the body. It is generally slimmer, lighter and more compact;
• brain. In migratory subjects there was a major development of the hippocampus.
These are differences that are easily explained: sharper wings and shorter tail substantially reduce aerodynamic drag during flight, and this implies the possibility, for the migrator, to fly more easily and with less energy expenditure. On the other hand, birds that have more rounded wings and longer tails have greater control and maneuverability during the ascent and take-off phase.
The length of the bones, which at first appears to be a detail not directly inherent in flight, is and how. Longer bones allow the formation of stronger muscles and therefore the possibility of withstanding heavier efforts.

Evolution of the species, a question of genetics.
When it comes to evolution in good measure, genetics is at the center. It is genetics that probably help them when it comes to leaving and returning to the same area, informing animals of the best time for breeding, helping them get to places they have never seen before. To demonstrate that it is not about magic but about genetics, a recent study, conducted by Peter Berthold and some of his students, has finally demonstrated scientifically how fundamental genetics in the whole question of migration is.

In fact, it has been shown that the genetic characteristics that control migration are hereditary: natural selection does nothing but make choices, very similar to those made by farmers who choose to reproduce the longest-lived and most productive plant. Natural selection for its part chooses to eliminate or safeguard the most useful genetic traits. Through this kind of choices the population changes more or less slowly. When it comes to migrants, specifically, the traits under hereditary genetic control are mainly 3: the migration times, the distance to be traveled and the direction of flight. Migration after migration, only the individuals with the best characteristics will survive and therefore pass on their genetic aptitudes to others.