Definition of Migratory Birds

The difference between migration in other groups of animals in general and what occurs in birds is primarily a matter of space-time scale. Although not all birds migrate, they all possess the characteristics and genetic information to be able to do so.

Migration, then, is a series of physiological and behavioral components that has been undergoing changes generation after generation and that these changes have occurred in order to adapt to changes between areas from

feeding, reproduction, climate changes, differences in the amount or location of bodies of water. What aspects are involved? Why do they do it? How have migratory patterns changed over time?

One of the main reasons is to find a better place to feed, where there is a greater variety and quantity of food and / or water sources available. Another reason for dispersion is due to seasonality, this means that due to climatic conditions the animals They move niche hoping to find environmental conditions more in line with the needs of each species. For its part, reproduction is one more reason for animals to decide to undertake a long way, either to find potential mates, to spawn or to find suitable places for the breeding.

The most likely reason that migration patterns have and continue to change over time is seasonal changes causing changes in turn in the food supply that in most cases has been expressed as a decrease in the quantity of it, as well as competition for space, couple and means.

Difference between heavy and light birds, in the efficiency and speed of flight

An important factor for migration is the size of the body, since this not only influences the weights that the wings must support during the flight, but also determines the reserves of fuel that the birds carry with them. Body size limits bird migration.

There is a directly proportional relationship between body size, efficiency and speed of the flight, and inversely proportional to the amount of biomass that can be transported. That is, the more amount of body mass, the cost of flight increases, as well as the efficiency and speed; but the amount of fuel (in relation to body weight) that can be carried decreases which translates into a reduction in the maximum possible range of nonstop flight. The conclusion This is why smaller birds are better adapted for long-distance migrations. And between the heaviest and the lightest bird species there is also a difference in the mode of flight, since the heaviest birds tend to migrate more frequently using glider flight, while lighter species also migrate using glider flight. flutter.

Therefore, the existence of thermals or other upward air currents is of greater importance for the birds. heavier compared to lighter birds and thus affects migration (especially route) (Heus, M. 2013).

Migratory routes

The migratory routes are perfectly established for each species of birds or for groups of them and it is probable that these routes have arisen due to directional preferences that were modified or established by selection natural.

Generally, birds do not travel in a straight line between the breeding and hibernation areas, because they prefer to avoid the energy and caloric expenditure between large crossings such as that which occurs from Europe to Africa, in the Mediterranean Sea and the desert of the Sahara. Many species of birds also do not use the same route each season, so it cannot be inferred that they have a preference for any particular route, however, it is believed that there are populations that use different routes because they can find different places for their reproduction and therefore they use the routes depending on the distance to travel.

Factors that affect the behavior of the species

The priority in the time of arrival to the breeding area allows that group to have control of the limited resources in the place of arrival and a consequent gain in productivity, and where members of one class have more to gain from early arrival than members of another, then the class with the most to gain would be expected to develop an immigration schedule and / or a non-reproductive distribution that promotes priority of arrival, provided the gain is large enough to offset any costs associated with that schedule or distribution.

Birds most at risk of predation are likely to migrate for social behavior, to save Energy and for reasons of security that are related to group travel. Individual behavior is expected to occur more frequently in raptors, for example, that migrate using thermals and therefore only expected in a concentrated number near the bottlenecks (Siepel, 2013).

Thus, arrival and social behavior are already two characteristics that seem to affect migration. However, there are many more, especially those that are needed to migrate in the first place, such as extraordinary navigation skills, bookings of massive body fuel for flights, coupled with continuous uninterrupted exertion for many hours at a time, cope with less oxygen in the thinner atmosphere, corrections for drift off course, travel duration influenced by body size, wing size and powers of flight (Alerstam 2001; Newton 2008), but also, for example, a larger immune system.

Bibliography

Alerstam, T. (2001) Detours in Bird Migration. Journal of Theoretical Biology 209: 319-331

Heus, Mark. (2013). Migration in birds: Why go, where to and how to get there.

Newton, I. (2008) The Migration Ecology of Birds. Elsevier, London, p 976

Siepel, H., & Van Turnhout, C. TO. M. (n.d.). unpublished data. dept. Animal ecology and ecophysiology UK Nijmegen and SOVON.

Topics in Migratory Birds