Bird migration is the seasonal journey undertaken by many bird species between breeding and wintering grounds. Over millions of years, environmental changes caused by ice ages shaped birds' migratory habits through natural selection. Physiological and environmental cues trigger migration, prompting birds to accumulate fat stores and prepare for long flights. Migration allows birds to access nesting and food opportunities while escaping harsh weather, lack of resources, and other threats. However, migratory birds now face increasing human threats including habitat destruction and pollution that hinder their long journeys.

1. Bird Migration
Submitted To:- Submitted By:-
Dr. Davinder Singh Harmanpreet Kaur
1351
M.Sc. (2nd Year) 3rd Sem.

2. 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

3. 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'.

4. 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

5. WHY BIRDS MIGRATE??
Migration as opportunity..
 Nesting
 Food
Migration as escape..
 From weather
 From lack of food
 Predators
 Diseases

6. WHEN AND HOW DO BIRDS MIGRATE?
 Environmental and physiology trigger
migration
 Circannual rhythm and daylight trigger
migration
 Weather influence bird migration
 Male go first

7. 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

8. 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

9. 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

10.  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

11. TYPES OF MIGRATION:
 Short distance migrants e.g. Hairy
woodpecker
 Medium distance migrants e.g. Eastern
Bluebird
 Long distance migrants e.g. Arctic Tern

12. 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.

13. 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.