Mystery of Migration

1. Mystery of Migration Devaka K Weerakoon Field Ornithology Group of Sri Lanka

2. Some of the animals in our surroundings are present throughout the year There are some birds that appear during a certain time and disappear again after a while which is repeated faithfully year after year Sometimes during certain months of the year we see large number of butterflies fly in the same direction

3. These observations have captured mans imagination raising questions such as Why do animals undertake such journeys? How do they find the way? In fact study of migration dates back to Aristotle (384 - 322 BC) In his book Historia Animalium he wrote that some creatures move south during winter to avoid the cold and return back during the spring. He also recognized that some migrate short distance while other travel a long way

4. Migration gave rise to lot of myths as well Aristotle proposed that some birds hibernate during the winter Aristotle was also responsible for theory of transmutation where he proposed some birds change into others (red start – Eurasian robin) with the arrival of the winter Barnacle/ Brent geese (Anser bernicla – the goose from barnacles)arose from Barnacles (Lepas antifera - the goose bearer) In 1955 Olaus Magnus, wrote that swallows spend winter under water

5. It is not possible to give a simple definition for the term migration Nature exist in infinite variety as does the phenomenon we refer to as migration making it impossible to capture it within a single common definition What is Migration?

6. Breeds in the north and winters in the southern hemisphere Barn Swallow (Hirundo rustica)

7. Found in North America Heads south to winter in Central America In spring it flies north again Few makes it back to where they started Monarch (Danaus plexippus)

8. Spawns in rivers of North America and Europe As they develop they drift down to the sea When they become adults they swim back to freshwater to breed Atlantic Salmon(Salmo salar)

9. Tiny microscopic animals that are at the bottom of marine food chains In summer they occupy the surface layer feeding on phytoplankton and breeding In winter they descend to deeper colder water and does not feed at all Zooplankton

10. All four are clear examples of migration and yet there are many differences Barn swallow – Seasonal movement over a long distance Monarch – Seasonal movement over long distance but does not complete the trip Salmon – Once in a life time journey over a long distance Zooplankton – Seasonal movement over short distance There are Commonalities and Clear Differences

11. Why Do Animals Migrate? • To avoid cold weather • To make use of an seasonal abundance of a food source • To Breed or spawn • To disperse or avoid crowding • Retreat to a place of safety • Slow down the metabolism • Avoid predators during early life stages

12. What Kind of Animals Migrate? • Zooplankton • Flatworms, star fish, lobsters, crabs

14. What Kind of Animals Migrate? • Zooplankton • Flatworms, star fish, lobsters, crabs • Insects Butterflies, locusts, aphids, social insects

16. What Kind of Animals Migrate? • Zooplankton • Flatworms, star fish, lobsters, crabs • Insects Butterflies, locusts, aphids, social insects • Fish – Salmon (Anadromous move from marine to freshwater), eel (catadromous – from freshwater to sea), move within marine habitat

18. What Kind of Animals Migrate? • Zooplankton • Flatworms, star fish, lobsters, crabs • Insects Butterflies, locusts, aphids, social insects • Fish – Salmon (Anadromous move from marine to freshwater), eel (catadromous – from freshwater to sea), move within marine habitat • Amphibians and reptiles • Birds

21. What Kind of Animals Migrate? • Zooplankton • Flatworms, star fish, lobsters, crabs • Insects Butterflies, locusts, aphids, social insects • Fish – Salmon (Anadromous move from marine to freshwater), eel (catadromous – from freshwater to sea), move within marine habitat • Amphibians and reptiles • Birds • Mammals

26. Human Migration

27. Classification of Migration • Complete migration - Cyclic event where the migrant travels along distance and returns to the original location • Partial migration – Short distance migration • Re-migration – migration cycle completed by off spring • Removal migration – One way movement

28. Types of Migration • North South Movements • East–west journeys • Circuits of the land and ocean • Trips up and down mountains • Vertical movements through the water column of seas and lakes

29. Where do they migrate and from to?

30. How do they Find the way? • Navigation vs Orientation • Navigation – Finding the way to a known location through unknown territory • Orientation– Finding the way to a known location through familiar territory • Navigation is done by • Sun, moon and stars • Routes learned from other birds • Detecting the earths magnetic field • Land marks – visual, olfactory, auditory

31. How do we study this Phenomenon? BANDINGUS Fish and Wildlife Service BirdBanding Laboratory RADAR (NOAA)Several years ago, researchers at Cape May counted 14 million birds in one night RADIO TELEMETRYCarl Safina followed a single radio-tagged albatross throughout its range SIGHTINGObservations using binoculars or a spotting scope

32. When do they Migrate? • Diurnal migrants • Most birds which rely on gliding or flap& glide flight are diurnal migrants • The chief benefit of daytime flight is thermals – rising currents of warm air that provide lift • Nocturnal migrants • Many birds which use powered flight are nocturnal migrants • Night flying helps birds avoid predators • The air is calmer and more stable at night

33. Where do birds spend their time while in Sri Lanka

34. Main Migratory Routes

35. Major “fly-ways” to the country

36. Principal Entry Points

37. Major routes of dispersal within the country

38. Some Record Migrations • The longest insect migration is the monarch butterfly. It travels up to 4,750km in the autumn. • The largest migrant is the blue whale. It reaches a length of 24-27m. • The longest recorded journey in water is a leatherback turtle, which travelled 20,558km in 647 days.

39. Bar-tailed Godwits have the longest known non-stop flight of any migrant, flying 11,000 km from Alaska to their New Zealand non-breeding areas.

40. Some Record Migrations • The highest migration is the bar-headed goose that can reach up to 9,000m altitude. • The Arctic Tern has the longest-distance migration of any bird, from its Arctic breeding grounds to the Antarctic non-breeding areas, a sea journey of over 22,000 km (14,000 mi).

41. What are the problems they face? • Habitat destruction – loss of resting areas • Hunting • Climate change • Changes in landscape • Dam construction