Mexico, Distrito Federal Tuesday February 17 2009 Address by the legitimate president of Mexico, Andres Manuel Lopez Obrador during the rally of the National Movement in Defense of the Popular Economy, in front of the Palacio Legislativo de San Lazaro. Ladies and gentlemen, thank you very much for coming back to this Assembly, I wholeheartedly thank you very much, because the presence of you, men and women is what strengthens our movement. Therefore we will not fail to recognize the effort, the sacrifice they make to attend these meetings. Many land birds migrate long distances. The most common pattern involves flying north to breed in summer in temperate or arctic areas and the return to wintering areas in warmer regions of the south.
The primary advantage of migration is energetic. The longer days of summer in the north to provide greater opportunities for breeding birds feed their chicks. The extension of the hours of the day allows diurnal birds produce larger clutches the related non-migratory species that remain in the tropics throughout the year. As the days get shorter in autumn, the birds return to the warm regions where the available food supply varies little with the station.
These advantages outweigh the risks of high stress, the energy cost, and other risks of migration. Predation may be increased during migration eleonorae Falco (Eleonora falcon) that breed on the islands of the Mediterranean breeding season is well behind schedule, coordinated with the autumn passage birds that migrate south from their feeding chicks . A similar strategy is adopted by the bat Nyctalus lasiopterus, which feed on migratory birds. The highest concentrations of migrant birds in stops transient sites also make them susceptible to parasites and pathogens, requiring a response Immune higher .
Within one species in particular, not all populations are to be migratory, which is called partial migracion. Migration is very common part in the continents of the south, in Australia, 44 of the species of passerine birds and 32 of migratory passerines are biased In some species the population of higher latitudes tends to be migratory and wintering latitudes more frequently in low latitudes where other populations of the same species are sedentary and therefore has already occupied that habitat suitable for wintering, and this is called “jumping frog migration.” 7 Within a population, we can have a different pattern of timing and migration based on age and sex. Only females of Fringilla coelebs (Chaffinch) in Scandinavia migrate and males remain as residents. This gave rise to the specific name coelebs, meaning single.
Most of the migrations begin with the birds taking off in a big forehead. In some cases involving migracion migracion narrow belts that are established as traditional routes known as migratory flight paths. These typically follow coastlines and mountain chains, and can take advantage of breezes and wind patterns or avoid geographical barriers such as large bodies of open water. The specific routes may be genetically programmed or learned in varied degrees. The routes taken in one direction and in return are often different .
Many of the largest flying birds in flocks. The fly also helps to reduce energy consumption. Many large birds flying in V formation and the individual energy savings are estimated at an amount of 12-20 . correlates Calidris canutus (correlative fat) and Calidris alpina (common correlates) were followed by study of radar while flying 5 km per hour faster than when flying in flocks alone .
The altitude at which birds fly during migration varies. An expedition to Mount Everest found skeletons of Anas acuta (pescuecilargo added rabudo or duck) and Limosa limosa (becasina or needle colinegra) at 5000 m above the Khumbu glacier. Geese Anser indicus were seen flying over the highest peaks 8000m on the Himalayas, even if there were some steps lower than 3000m. Seabirds fly low over the water but they gain altitude when crossing land and on a reverse pattern is seen in terrestrial birds. However most bird migration occurs in the range from 150 m to 600 m. Records bird collisions in the United States show that most of the impacts occur at altitudes below 600 m and almost none above 1800 m.
Most species make migrations ping INOS regular swimming. These routes can cover more than 1000 km. Dendragapus obscurus (Rooster of the Rockies) performs altitudinal migrations walking for the most part. The emus in Australia have been observed making walking long distances during droughts.
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