Mystery of Migration
and wetland wildlife at
Sungei Buloh Nature Park
A few birds fly non-stop, some for several days, covering enormous distances.
But most birds break journey at staging posts. A vital aspect of being able
to make such long trips is to lay down enough fat reserves. This is why
staging posts such as Sungei Buloh are important to migrating birds.
do birds migrate?
The reasons are complex and not fully understood. But a simple explanation
is food and a safe place to breed. Birds which breed in the summer
in the extreme north such as the Arctic benefit from an abundance
of food as plants and insect life flourish in the long daylight hours;
and because few large permanent predators can survive the harsh winter.
Many birds that breed in the Arctic simply lay their eggs on the ground.
Being able to fly, they can avoid the harsh winter conditions, and
be the first to arrive to enjoy the summer benefits.
fact, some have suggested that the question should be why don't all
birds migrate. Flight gives birds a huge advantage in finding new
sources of food and good places to breed, that it is strange that
not more birds migrate.
did bird migration routes become established?
Migration is affected not only by food supply, but also by wind and
oceans currents. These make some routes and locations easier to reach.
While many birds migrate from northern breeding areas in the summer,
to southern wintering grounds (mainly because there is more land near
the northern pole than the southern), there are many other migration
patterns. Some birds breed in the far south of South America, Australasia
and Africa, and migrate to northern wintering grounds. Some birds
migrate horizontally, to enjoy the milder coastal climates in winter.
Other birds migrate in terms of altitude; moving higher up a mountain
in summer, and wintering on the lowlands.
kinds of birds migrate, from large cranes, birds of prey, to tiny
hummingbirds. Even flightless birds migrate! Emus move from breeding
sites in the rainy season to more permanent water sources in the dry.
Penguins migrate in the ocean. Auk babies migrate by swimming until
they fledge and can fly! Even birds that spend their entire non-breeding
time in flight, such as seagulls, also move around on the ocean to
follow seasonal food abundances.
|How do birds migrate such long
Birds exploit the winds to their favour so they can go the distance
by burning minimal fuel. They may shift altitude to find the best
wind "conveyor belt". Winds at high altitude may blow in
the opposite direction from wind on the ground, and usually are blowing
strongly. Larger birds rely on thermals (hot air) rising from the
ground in the mornings to gain altitude by simply soaring. These birds
usually migrate during the day. They may also follow strong updrafts
The longest migration is undertaken
by the Arctic Tern (Sterna paraisaea). It breeds in
the Arctic North in the summer, then flies all the way to the other
pole to spend winter on the Antarctic ice pack. The shortest distance
between the two poles is 15,000km, but the birds usually travel a
more circuitous route and can cover up to 20,000km; making a round
trip of 30-40,000km!
for the journey: Besides
laying down fat reserves, migrating birds also need to eat a lot to fuel
their regular feather moults. Their feathers must be in tip-top condition
for their long trips. Different species moult at different times; for most
shorebirds it is just after breeding and before the migration to wintering
How do migrating birds find their way?
Studies suggest birds orientate themselves to the compass points using the
position of the sun during the day, and the stars at night. They can also
sense magnetic north. In addition they use other clues such as visual layout
of the land, smell (of the sea), sound (waves on shores, winds through mountain
The most amazing aspect of bird migration is that the location, route and
perhaps even the techniques are hard-wired into their brains. Many migrating
birds abandon their young as soon as they fledge, and a short time later,
the young make the migration on their own.
Threats to migrating birds: Sadly, in
addition to surviving storms and bad weather, exhaustion and other natural
obstacles, migrating birds are increasingly face human threats. Habitat
destruction that affects staging posts handicap their ability to re-fuel.
These include draining wetlands, cutting down forests. Pollution of the
sea, water and air also affects them. Migrating birds are also distracted
and killed by lit-up skyscrapers, lighthouses and other unnatural man-made
formations that mislead them. Sadly, many migrating birds are also hunted,
for food, and for sport or superstitious reasons.
Websites on the East Asian Flyway
Ireland: Migration-changing with the seasons: excellent explanation
of migration with maps of migration in Europe and Africa; and excellent
illustrations of how birds migrate plus details of experiments to highlight
their talents; the effects of man on bird migration.
Prairie Wildlife Research Center: Migration of Birds, based on the
book by by Frederick C. Lincoln; Tons of details about bird migration
in the Americas; origin and evolution, how scientists study bird migration,
migration routes and patterns, and lots lots more.
Why Files: lots of details about bird migration in the Americas;
why and how they do it and threats to migratory birds.
lots of details about why and how birds migrate, with examples, details
and maps about migration in the Americas.
Society: Bird Migration Facts with lots of details on why wetlands
are crucial for migrating birds.
National Aviary: a brief description of why birds migrate.
Gum on the Australian Broadcasting Corporation website: links to
waders and the East Asia Flyway
- Jonathan Elphick (ed.), "Collin Atlas of Bird Migration:
Tracing the Great Journeys of the World's Birds", Harper
- David Attenborough,
"The Life of Birds", Princeton University Press, 1998.