FOGSL Mystery of Migration Devaka K Weerakoon Field Ornithology Group of Sri Lanka

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Mystery of MigrationMystery of Migration

Devaka K WeerakoonDevaka K Weerakoon

Field Ornithology Group of Sri Field Ornithology Group of Sri LankaLanka

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•Some of the animals in our Some of the animals in our surroundings are present throughout surroundings are present throughout the yearthe year

•There are some birds that appear There are some birds that appear during a certain time and disappear during a certain time and disappear again after a while which is repeated again after a while which is repeated faithfully year after yearfaithfully year after year

•Sometimes during certain months of Sometimes during certain months of the year we see large number of the year we see large number of butterflies fly in the same directionbutterflies fly in the same direction

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•These observations have captured mans These observations have captured mans imagination raising questions such asimagination raising questions such as

– Why do animals undertake such Why do animals undertake such journeys?journeys?

– How do they find the way?How do they find the way?

•In fact study of migration dates back to In fact study of migration dates back to Aristotle (384 - 322 BC)Aristotle (384 - 322 BC)

•In his book In his book Historia AnimaliumHistoria Animalium he wrote he wrote that some creatures move south during that some creatures move south during winter to avoid the cold and return back winter to avoid the cold and return back during the spring. He also recognized that during the spring. He also recognized that some migrate short distance while other some migrate short distance while other travel a long way travel a long way

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•Migration gave rise to lot of myths as wellMigration gave rise to lot of myths as well

•Aristotle proposed that some birds Aristotle proposed that some birds hibernate during the winterhibernate during the winter

•Aristotle was also responsible for theory of Aristotle was also responsible for theory of transmutation where he proposed some transmutation where he proposed some birds change into others (red start – birds change into others (red start – Eurasian robin) with the arrival of the Eurasian robin) with the arrival of the winterwinter

•Barnacle/ Brent geese (Barnacle/ Brent geese (Anser bernicla – Anser bernicla – the the goose from barnacles)goose from barnacles) arose from arose from Barnacles (Barnacles (Lepas antiferaLepas antifera - the goose - the goose bearer)bearer)

•In 1955 Olaus Magnus, wrote that swallows In 1955 Olaus Magnus, wrote that swallows spend winter under water spend winter under water

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•It is not possible to give a simple It is not possible to give a simple definition for the term migration definition for the term migration

•Nature exist in infinite variety as does Nature exist in infinite variety as does the phenomenon we refer to as the phenomenon we refer to as migration making it impossible to migration making it impossible to capture it within a single common capture it within a single common definition definition

What is Migration?What is Migration?

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•Breeds in the north and winters in Breeds in the north and winters in the southern hemispherethe southern hemisphere

Barn Swallow Barn Swallow ((Hirundo rusticaHirundo rustica))

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•Found in North AmericaFound in North America

•Heads south to winter in Central Heads south to winter in Central AmericaAmerica

•In spring it flies north againIn spring it flies north again

•Few makes it back to where they Few makes it back to where they startedstarted

Monarch Monarch ((Danaus plexippusDanaus plexippus))

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•Spawns in rivers of North America and Spawns in rivers of North America and EuropeEurope

•As they develop they drift down to the As they develop they drift down to the seasea

•When they become adults they swim When they become adults they swim back to freshwater to breedback to freshwater to breed

Atlantic SalmonAtlantic Salmon((Salmo salarSalmo salar))

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•Tiny microscopic animals that are at the Tiny microscopic animals that are at the bottom of marine food chainsbottom of marine food chains

•In summer they occupy the surface In summer they occupy the surface layer feeding on phytoplankton and layer feeding on phytoplankton and breedingbreeding

•In winter they descend to deeper colder In winter they descend to deeper colder water and does not feed at allwater and does not feed at all

ZooplanktonZooplankton

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•All four are clear examples of migration and All four are clear examples of migration and yet there are many differencesyet there are many differences

•Barn swallow – Seasonal movement over a Barn swallow – Seasonal movement over a long distancelong distance

•Monarch – Seasonal movement over long Monarch – Seasonal movement over long distance but does not complete the tripdistance but does not complete the trip

•Salmon – Once in a life time journey over a Salmon – Once in a life time journey over a long distancelong distance

•Zooplankton – Seasonal movement over short Zooplankton – Seasonal movement over short distancedistance

There are Commonalities and There are Commonalities and Clear DifferencesClear Differences

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Why Do Animals Why Do Animals Migrate?Migrate?

•To avoid cold weatherTo avoid cold weather

•To make use of an seasonal abundance of a To make use of an seasonal abundance of a food sourcefood source

•To Breed or spawnTo Breed or spawn

•To disperse or avoid crowding To disperse or avoid crowding

•Retreat to a place of safetyRetreat to a place of safety

•Slow down the metabolismSlow down the metabolism

•Avoid predators during early life stagesAvoid predators during early life stages

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What Kind of Animals What Kind of Animals Migrate?Migrate?

•ZooplanktonZooplankton

•Flatworms, star fish, lobsters, crabsFlatworms, star fish, lobsters, crabs

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•Insects Butterflies, locusts, aphids, social Insects Butterflies, locusts, aphids, social insectsinsects

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•Fish – Salmon (Anadromous move from Fish – Salmon (Anadromous move from marine to freshwater), eel (catadromous – marine to freshwater), eel (catadromous – from freshwater to sea), move within marine from freshwater to sea), move within marine habitathabitat

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•Amphibians and reptilesAmphibians and reptiles

•BirdsBirds

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•Amphibians and reptilesAmphibians and reptiles

•BirdsBirds

•MammalsMammals

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Human Migration

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Classification of MigrationClassification of Migration

• Complete migration - Cyclic event where the Complete migration - Cyclic event where the migrant travels along distance and returns migrant travels along distance and returns to the original locationto the original location

• Partial migration – Short distance migration Partial migration – Short distance migration

• Re-migration – migration cycle completed by Re-migration – migration cycle completed by off springoff spring

• Removal migration – One way movementRemoval migration – One way movement

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Types of MigrationTypes of Migration

• North South MovementsNorth South Movements

• East–west journeysEast–west journeys

• Circuits of the land and oceanCircuits of the land and ocean

• Trips up and down mountainsTrips up and down mountains

• Vertical movements through the water Vertical movements through the water column of seas and lakescolumn of seas and lakes

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Where do they migrate and from Where do they migrate and from to?to?

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How do they Find the How do they Find the way?way?

• Navigation vs OrientationNavigation vs Orientation

• NavigationNavigation – Finding the way to a known – Finding the way to a known location through unknown territorylocation through unknown territory

• OrientationOrientation – – Finding the way to a known Finding the way to a known location through familiar territorylocation through familiar territory

• Navigation is done byNavigation is done by

•Sun, moon and starsSun, moon and stars

•Routes learned from other birdsRoutes learned from other birds

•Detecting the earths magnetic fieldDetecting the earths magnetic field

•Land marks – visual, olfactory, auditory Land marks – visual, olfactory, auditory

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How do we study this How do we study this Phenomenon?Phenomenon?

SIGHTINGObservations using binoculars or a spotting scope

BANDINGUS Fish and Wildlife Service BirdBanding LaboratoryRADAR (NOAA)Several years ago, researchers at Cape May counted 14 million birds in one nightRADIO TELEMETRYCarl Safina followed a single radio-tagged albatross throughout its range

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When do they When do they Migrate? Migrate?

Diurnal migrantsDiurnal migrants

• Most birds which rely on gliding or flapMost birds which rely on gliding or flap& glide flight are diurnal migrants& glide flight are diurnal migrants

• The chief benefit of daytime flight is The chief benefit of daytime flight is thermals – rising currents of warm air thermals – rising currents of warm air that provide liftthat provide lift

Nocturnal migrantsNocturnal migrants

• Many birds which use powered flight are Many birds which use powered flight are nocturnal migrantsnocturnal migrants

• Night flying helps birds avoid predatorsNight flying helps birds avoid predators

• The air is calmer and more stable at The air is calmer and more stable at nightnight

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Where do birds spend Where do birds spend their time while in Sri their time while in Sri

LankaLanka

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Main Migratory Routes

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Major “fly-ways” to the country

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Principal Entry Principal Entry PointsPoints

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Major routes of Major routes of dispersal within dispersal within the countrythe country

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Some Record Some Record MigrationsMigrations

• The longest insect migration is the monarch The longest insect migration is the monarch butterfly. It travels up to 4,750km in the butterfly. It travels up to 4,750km in the autumn.autumn.

• The largest migrant is the blue whale. It The largest migrant is the blue whale. It reaches a length of 24-27m.reaches a length of 24-27m.

• The longest recorded journey in water is a The longest recorded journey in water is a leatherback turtle, which travelled 20,558km leatherback turtle, which travelled 20,558km in 647 days.in 647 days.

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

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Some Record Some Record MigrationsMigrations

• The highest migration is the bar-headed The highest migration is the bar-headed goose that can reach up to 9,000m altitude.goose that can reach up to 9,000m altitude.

• The Arctic Tern has the longest-distance The Arctic Tern has the longest-distance migration of any bird, from its Arctic migration of any bird, from its Arctic breeding grounds to the Antarctic non-breeding grounds to the Antarctic non-breeding areas, a sea journey of over breeding areas, a sea journey of over 22,000 km (14,000 mi).22,000 km (14,000 mi).

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What are the problems What are the problems they face?they face?

• Habitat destruction – loss of resting areasHabitat destruction – loss of resting areas

• HuntingHunting

• Climate changeClimate change

• Changes in landscapeChanges in landscape

• Dam constructionDam construction

Documents

FOGSL Mystery of Migration Devaka K Weerakoon Field Ornithology Group of Sri Lanka