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Pres birds


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Pres birds

  1. 1. Bird migration Made by: Lilly and Eirik 08.04.2014
  2. 2. Skilt langs stien ved Borrevannet.08.04.2014
  3. 3. Why do some birds migrate, and how do they fly • Some birds migrate because they are looking for areas with access to food. • Norway is a good food source for birds, and especially in Borre Vestfold. The waters in Borre are an ideal place for over 230 different bird species. Borrewater provides good food so the birds can feed up themselfes before winter or migration. • By flying in the plow formation the birds totally get 71% more flying capacity. 08.04.2014
  4. 4. • Flocks of birds perform some aerial phenomena, which have amazed many of its viewers. This thesis is a literature review, which concerns the three major questions of ‘When’, ‘How’ and ‘Why’ birds fly in flocks. Flying flocks are roughly dividable in two types: ball shaped clusters and line formations. Whereas cluster flying is commonly used throughout the year by groups of birds, for example while transiting between their roosting and their foraging sites, formation flight is almost specifically used for migration. The departure time of migration is a critical moment in the annual cycle of the bird. The exact moment of departure is an optimization of several external and internal factors, including migrating distance, energy reserves and weather conditions. Clusters have a three-dimensional structure and tend to be rather disorganized. When a predator is nearby, clusters often start to perform rapid manoeuvres. Previously believed to be coordinated by telepathy or electromagnetic communication, due to high-speed filming scientists have determined that these manoeuvres are initiated by one individual bird and followed by the rest of the flock. The individual fulfilling the role of initiator changes from moment to moment. The most likely explanation for movement in a cluster is a self-organization mechanism where each bird applies a few behavioural rules in response to local information from neighbouring birds. There are different kinds of formations, ranging from an acute V-formation to a U-shaped bow. Although the total energy saving is the same for different formations, it differs for individual birds in the group. In an acute formation, the leader gains little or no energy savings, while in a U-formation the energy savings are more egalitarian. A reason for obtaining a specific formation may be related to kin-selection or reciprocity, although no empirical evidence for this hypothesis has been found yet. Several specific reasons have been put forward for birds to fly in clusters, mainly regarding predation prevention. These advantages include increased predator detection, a dilution effect, physical protection of neighbours and a confusion effect. Two hypotheses exist for a structured formation, like the well known V-shape. One is the aerodynamic advantage hypothesis, in which birds conserve energy by taking advantage of the upwash vortices created by the wings of the birds in front. The other is the communication and orientation hypothesis, in which birds make use of their position for their combined orientation experience and visual communication. These explanations are not mutually exclusive, and various studies have given support to both of them. However, no conclusive evidence has been found for any of the both hypotheses. There is still a debate going on between supporters and criticasters of both hypotheses which remains unsolved upon till now. A review of the literature concerning the subject of flock flying shows that the use (the ‘When’) and the organization (the ‘How’) of flock flying have been thoroughly researched, which has led to a consistent view on these subjects. However, thorough research on the main reasons for flock flying (the ‘Why’) has not given a clear view yet. Also behavioural aspects of the organization and departure are still shrouded. These subjects still raise enough questions to provide research options for years to come. 08.04.2014
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  6. 6. How they find their way 08.04.2014
  7. 7. • For thousands of years, homing pigeons were the most sophisticated means of long-distance communication. The winners of the first Olympics were announced by homing pigeon. Julius Reuter started his news service with them. Cher Ami, an avian member of the U.S. Army Signal Corps, received the Croix de Guerre in World War I after completing a mission with a bullet in his breast. • How do the birds find their way home? Decades of studies with frosted lenses, magnetic coils or scent deprivation show they use pretty much every clue available. The most difficult one for us to comprehend may be the earth’s magnetic field. Birds see it, but what it looks like to them, nobody knows. Work by Roswitha and Wolfgang Wiltschko in Germany, among others, suggests that this sense relies on quantum mechanics—that is, birds detect something happening in the eye at a subatomic level. Light striking the retina seems to stimulate chemical reactions that produce pairs of molecules with electrons that are “entangled,” meaning they share certain quantum properties. One of those properties, called “spin,” is affected by a magnetic field. That effect could tell the bird which way is north. • Charles Walcott of Cornell, who began studying pigeons in the 1960s, says homing is “still a mystery” 08.04.2014
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  9. 9. Why do some birds arrive early and others late? • The migrants comes back in different times during the spring. The ones that are close, like Denmark, can come early and return to Denmark if the weather is not as they expected. • For example the migration of the ”beek gees” (nebbgjess), north in Denmark to Svalbard. We know that they fly about 50-60 km/h, and so we can find out from the the time they leave Denmark when they will arrive in Borre. 08.04.2014
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  11. 11. The birds who don’t migrate • Birds survive the winter by first thickening their feather layer , eating berries and seeds that they find.Through evolution their beek have shortened and become thicker to suit the climate. All birds fly longer or shorter distances even if they don’t migrate. 08.04.2014
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  13. 13. Sometimes colours and other artefacts are seemingly dangerous to the male bird. Still they have it. Why? • To be visible for the females and to attract them. 08.04.2014
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  15. 15. What is a bird and who are their ancestors? • The discovery that birds evolved from small carnivorous dinosaurs of the Late Jurassic was made possible by recently discovered fossils from China, South America, and other countries, as well as by looking at old museum specimens from new perspectives and with new methods. The hunt for the ancestors of living birds began with a specimen of Archaeopteryx, the first known bird, discovered in the early 1860s. Like birds, it had feathers along its arms and tail, but unlike living birds, it also had teeth and a long bony tail. Furthermore, many of the bones in Archaeopteryx's hands, shoulder girdles, pelvis, and feet were distinct, not fused and reduced as they are in living birds. Based on these characteristics, Archaeopteryx was recognized as an intermediate between birds and reptiles; but which reptiles? In the 1970s, paleontologists noticed that Archaeopteryx shared unique features with small carnivorus dinosaurs called theropods. All the dinosaur groups on this evogram, except the ornithischian dinosaurs, are theropods. Based on their shared features, scientists reasoned that perhaps the theropods were the ancestors of birds. When paleontologists built evolutionary trees to study the question, they were even more convinced. The birds are simply a twig on the dinosaurs' branch of the tree of life. • As birds evolved from these theropod dinosaurs, many of their features were modified. However, it's important to remember that the animals were not "trying" to be birds in any sense. In fact, the more closely we look, the more obvious it is that the suite of features that characterize birds evolved through a complex series of steps and served different functions along the way. • Take feathers, for example. Small theropods related to Compsognathus (e.g., Sinosauropteryx) probably evolved the first feathers. These short, hair-like feathers grew on their heads, necks, and bodies and provided insulation. The feathers seem to have had different color patterns as well, although whether these were for display, camouflage, species recognition, or another function is difficult to tell. 08.04.2014
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  17. 17. 08.04.2014 Litterature list: