Bird Migration

Submitted To:- Submitted By:-Dr. Davinder Singh Harmanpreet Kaur

1351M.Sc. (2nd Year) 3rd Sem.

MIGRATION OF BIRDS:

Migration is the yearly, seasonal journey

undertaken by many species of birds. During

this journey, birds cover distances of many

kilometers. Most common type of migration

carried out by birds in spring and autumn.

BREEDING GROUNDS

WINTERING GROUNDS

HOW DID MIGRATION ORIGINATE?

Roots of migratory habits of modern birds are

believed to date back millions of years and were

tempered by environmental changes caused by

the ice Ages of Quaternary period over the last

2,500,000 years.

As environment changed, some animals

changed their habitat slightly towards more

favourable places. Then stabilized by natural

selection. Thus natural selection favoured the

' migrants'.

STIMULUS FOR MIGRATION:

Certain physiological and environmental

cues,such as in late summer decrease in sunlight

stimulate s migratory bird's pituitary gland to

produce harmones prolactin and corticosterone

from adrenal gland. These cause birds to:

accumulate large amount of fat

provide enough energy for long

WHY BIRDS MIGRATE??

Migration as opportunity..

Nesting

Food

Migration as escape..

From weather

From lack of food

Predators

Diseases

WHEN AND HOW DO BIRDS MIGRATE?

Environmental and physiology trigger

migration

Circannual rhythm and daylight trigger

migration

Weather influence bird migration

Male go first

HOW DO BIRDS MIGRATE SUCH LONG

DISTANCES?

Birds exploit winds to their favour

A vital aspect of being able to make such

long trips is to lay down enough fat reserves

Preparing for journey..

Bar-tailed Godwit flies 1100 km from

Alaska to New Zealand

Timing

Energy for the flight

Survival of the fittest

Energy saving

WHERE TO GO AND HOW TO GET

THERE?

Navigation strategies

Detecting magnetism

Magnetic field: an imperfect

aid

Information from sky

Cross-referencinh

Using sight, sound, smell

Silvereye

Earth's magnetic field

Celestial rotation

MIGRATORY ROUTES:

Each migratory species has its own characteristics

routes between its nesting and winter ranges. These

paths are often rather broad.

Water fowl have more restricted path

Some birds show other general paths

e.g. In North America, many songbirds and

shorebirds follows an elliptical path

waterfowl

The third dimension e.g.Hawks and vultures migrate at 3000 feet or less.

e.g.Some migrate at extremely high altitude like Bar-headed

Geese at 27880 feet

Site ffidelity Bobolink exceed 12000 miles in a year, yet their site fidelity is

quite strong.

Important stopover locations Redknot stop on the shores of Delaware Bay to refuel before

continuing journey to their breeding ground on Arctic Tundra

TYPES OF MIGRATION:

Short distance migrants e.g. Hairy

woodpecker

Medium distance migrants e.g. Eastern

Bluebird

Long distance migrants e.g. Arctic Tern

BENEFITS OF MIGRATION:

Avoid harsh and dangerous winter climates.

Avoid lack of food during winter.

especially insectivorous birds such as

wood warbles and fruit eating birds such as

waxwing.

Avoid lack of cover during winter.

Migrate from area of sparse or no food to

area of relatively abundant food.

THREATS TO MIGRATORY BIRDS:

Sadly, in addition to surviving storms and bad

weather, exhaustion and other natural obstacles,

migratory 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 sea,water and air also effects them.

These are also killed by lit-up skyscrapers,

lighthouses etc.