MIGRATION IN BIRDS by Shraddha Gupta.pptx

the migratory behaviour of birds is discussed

1. Migration In Birds By:- Shraddha Gupta
M.Sc. Final Zoology Bareilly College, Bareilly

2. What is Migration? The migration is movement of a population of organisms from one environment to another. The word “ migration” has been derived from Latin “ Migrare ” meaning to go from one place to another. It is a sort of periodic and directed travel due to changes in environmental conditions. Thus, we can define migration as much directional movement of large number of a species from one habitat or location to another.

3. Migration in birds The birds migration is seasonal movement from one habitat to another and back again to get the advantage of favourable conditions . It is traditionally, hereditary [instinctive] and of regular occurrence at definite interval every year.

4. Adaptation in birds for flying • Birds have several unique features that allow them to fly.

- wings to produce flight

- strong flight muscles to move the wings

- active metabolism that provides energy to the muscles

- hollow bone structure to minimize weight

- gonads active during only part of year

5. Migratory status A migrating bird is called a migrant . Depending on the seasons of migrants of different birds, different names are given to the migrants. These are as follows:- Winter visitors Summer visitors Transient visitors or passage migrants Permanent residents

6. 1. Winter visitors [North ↔️South]:- Includes those species which move from their breeding grounds to spend their winter in the most suitable places where food is also in plenty. For example, •Field fare, snow bunting and redwing arrived in autumn chiefly from the north stay throughout the winter and fly northwards in spring. •Greylag goose, Pintail, Common teal, European starling are the winter visitors visiting Keoladeo National park Bharatpur . 2.Summer visitors [South ↔️ North]:-From spring onwards, south starts getting too hot while luxurious summer conditions prevail in the north. The birds of south leave it in spring for North to spend the summer, breed and return to south again in autumn, when the north gets cold. For example, • the Cuckoo [ Eudynamis scolopaccus ] arrives in Uttar Pradesh in the beginning of March and breeds there. During the month of August it leaves this place and migrates to South India and Ceylon to spend winter there. Snow bunting Cuckoo

7. 3. Transient visitors or passage migrants :-Summer and winter visitors while migrating from South to North and vice versa, stop at some places for the sake of rest only. For example, • Gargany teals migrate from Mongolia or Siberia to Bharatpur to go south India which is their actual breeding ground. While returning they again stop over at Bharatpur . 4.Permanent residents :-These birds are found in a particular area throughout the year and do not migrate from one place to another. For example, •Cotton teal, spot billed duck, whistling teal, warheaded goose, mallards, comb duck are all permanent resistant of Keoladeo National park, Bharatpur . Gargany teal Cotton teal

8. Types of migration 1. Daily Migration :-🔸Many birds make daily movements from their nest in response to environmental forces. 🔸 Daily migrations from their resting sites to feeding areas. For examples, crows, house sparrows, starlings, rockery herons, etc. 2.Local Migration :-🔸Local migration occurs because of heavy rain, flood,excessive cold &hot. 🔸Return to that area when crisis is over. 🔸Flowering of certain plants and ripening of fruits also cause local migration. 3.Seasonal migration :- 🔸Response to change in the season. 🔸In tropical & sub tropical area, this occurs in the beggining or end of the warm season. 🔸In temperate area ,the movement is triggered by onset of winters. 🔸 Such migration of birds are known in Northern hemisphere, Europe, North America and Asia.

9. 4.Moult Migration :-In most ducks, males and juvenile birds migrate short distances northward for moulting leaving behind females and young birds in the breeding grounds. 5.Cyclic Migration :-Migration of birds are seasonal, but do not occur at regular intervals. Eg : Snowy owl in search of lemming in U.S. in winter is occurs in 3 – 5 years. 6.Partial Migration :-All the birds of migratory bird do not leave the native land and hence are always represented by certain individuals. Eg : finch,titmouse,redbreast,songthrus etc. 7.Vagrant or Irregular Migration :-🔸Sometimes some birds disperse for a short or long distance for the sake of food and safety. 🔸The birds can also swept away by powerful wind and hurricanes to very long distances.

10. 8.Altitudinal or Vertical Migration :-🔸The birds living at high altitudes descends at lower altitudes in winter to save them selves from intense cold of high altitude . 🔸They return again to high altitudes with advent of summer. 🔸 In certain cases, such as Blue Grouse of USA, the direction of migration is reversed with the season. It passes winter high up in the rocky mountains probably to avoid competition and predators. 9.Latitudinal or Equatorial Migration :-The most familiar migration are those from north to south and vice versa. Eg;golden plover, cuckoo and storks pass summer in Northern hemisphere and winter in South. 10.Longitudinal Migration :- Movement of birds from east to west or vice versa. For example, evening grossbeaks that nest in Northern Michigan spend the winter in New England.

11. Diurnal and Nocturnal Migration On the basis of their wing powers and methods of getting food William brewster divide the birds into following three categories:- 1.Night Fliers :-Small birds such as passerine birds[sparrows, titamic , jays, crows etc.], cuckoos and wood pickers. Darkness provides them protection from large predatory birds and give birds opportunity of using all the daylight hours for feeding. 2.Day Fliers :- Large birds such as hawks, pigeons, swallows and robbins etc. Usually restless and strong winged and can feed while on wings having least danger of enemies and can migrate to long distances. 3.Few birds such as geese and ducks migrate both by day and night.

12. Bird migration does not always takes place by means of flight • Penguins breeds on the land of Antarctica continent. • They do so because during the fall Emperor Penguins mate and the female lays an egg. • They migrate inland away from water as the egg hatches. • So that there is more ice under the newborn penguin’s feet and much less chance of it falling through into the ocean.

13. Range of migration •The distance travelled by migratory birds depend upon the local conditions and the species concerned. •The longest distance of about 17600 kilometres is covered by the Arctic tern[ Sterna paradise] which migrates from North to edge of Antarctica. •Likewise golden plover migrates from the Arctic Tundra migrates to the pampus of Argentina. •The most spectacular of all migrant in Europe is white strok . Storks spend summer in Europe but spend the winter in South Africa. Arctic tern

14. Altitude of migration It thought that the birds are travelled very high & very fast speed. Recent knowledge obtained by Telescope
Radar Radiotelemetry pointed out that some birds fly at sea level. Some fly very close to the height of mount everest . Most birds fly less than 7400 feet above sea level.

15. Flying speed during migration Flying speed is measured by doppler radar. Speed ranged from 32-64 kmph in small song birds. Larger birds ,such as cranes 40-96 kmph. Perching birds can fly 32-59 kmph. Falcons, ducks, geese fly at speed of 77- 96kmph. Humming bird fly 32 kmph. Sandpipers fly 96 kmph. Doppler Radar

16. Causes of Migration Shortage of food supply on the breeding ground :- With the end of Summer in the Northern hemisphere, food supply falls short due to increase in the number of birds and secondly due to beginning of hibernation of insects. Environmental factors :- Fall and rise in the temperature change the endocrine state and metabolic conditions of the birds in such a way as to cause migration. Photoperiodism :- The day length affects pituitary and pineal body in the brain which in turn prepare word for migration. The migratory restlessness is initiated from this stage. Fat deposition :- According to Wolfson the substantial subcutaneous and visceral fat deposits play an important role in migration of the species. Fat provides metabolic water as well as energy in route.

17. Navigation Navigation is a means of determining the direction of a familiar goal across an unfamiliar area. By many methods researcher have show that pigeons other birds and animal are sensitive to the following stimuli:- Sun compass cues. Star compass cues. Magnetic and Gravity cues. Infrasound cues. Odours. Etc.

18. Sun compass cues :- Sun is used as a simple compass and that only its azimuth provides information for orientation. The migrating animals have to you know what time of day it is in order to use a sun as a compass. (ii) Star compass cues :- Use by night fliers. Ex. Indigo bunting moves between breeding sites in the Eastern half of the United States to a wintering home in Central Mexico for the Caribbean Island in a series of night time flights. (iii) Magnetic and Gravity cues :- Animals show festivities to magnetism as well as they often respond to gravitational cues (iv) Infrasound cues :- Sound with a frequency of less than 10 hertz is called infrasound humans cannot hear it but words can detect infrasonic frequency as low as 0.60 Hertz. It can travel many hundreds even thousands of kilometres thus allowing words to orientate to distant mountains or shorelines.

19. Methods of Study of Bird Migration Banding or Ringing :- It involves the use of coloured metal or plastic leg bands, systematically numbered and having the address of the branding agency to which the recovery of the branding work may be reported . The birds are first caught or trapped alive in large number by using mist nest or boom-net . This is thrown into air by explosives and spread out by metal weights which source over a flock of birds. By collecting dead migratory birds killed at television towers or by airport ceilometres or other human made high towers and poles interfering with migration. By tape recording aur chip counting. Radio tracking. Miniature transmitters weighing 2-3 gram, easily carried by small birds send a signal that may then be located by means of stationary direction finding aerials or by vehicles and aeroplanes.

20. Advantages of migration Securing a better climate for living by avoiding unfavorable climatic condition (intense cold, hot, stromy conditions ) & food shortage by migrating. By alternately exploiting 2 diifferent habitat for food due to migration , more birds can able to exist. Change in habitat provides greater variety in bird diet. Long summer days provide birds with long working hours to gather food to feed young ones. Predation pressure is less because it arrives in large numbers in breeding ground ,so it help in their survival.

21. Disadvantages of migration Migration is disadvantages to the birds in the following ways:- Natural hazards : • Climate changes • Drought • Food Supply • Predators • Physical demands of migration • Journey is tiresome for the birds and most of the passive bird succumb at sea Man-made hazards : • Barriers (fences, dams, & skyscrapers) • Water, aircraft, & fishing practices • Telegraphic wires,towers,light houses. The young and defenceless birds are exposed to various natural enemies birds and hunters.