1. Why do birds migrate?
Migration is a strategy to take advantage of seasonally abundant food supplies
Weather and photo-period are triggers
DEC
NOV
JAN
OCT
FEB
SEP
MAR
AUG
APR
MAY
SNOW BUNTING

2. MIGRATION STRATEGIES
Complete Migration
Cerulean warbler
Wilson’s plover
Stilt sandpiper
All individuals leave the breeding area after raising their families
Most complete migrants breed in temperate northern climates
Many complete migrants travel incredible distances between breeding and non-breeding habitats

3. MIGRATION STRATEGIES
Partial Migration
Red-tailed hawk
Herring gull
Bewick’s wren
Seasonal movement by some, but not all, individuals away from breeding area
Some overlap of breeding & non-breeding ranges

4. How do we study migration?
BANDING US Fish and Wildlife Service Bird Banding Laboratory
RADAR (NOAA) Several years ago, researchers at Cape May counted 14 million birds in one night
RADIO TELEMETRY Carl Safina followed a single radio-tagged albatross throughout its range
MOON WATCHING Requires a full moon, a comfortable chair and binoculars

5. How do we study migration?
CHRISTMAS BIRD COUNT
52,471
Number of participants

6. THE BASICS OF FLIGHT
Anatomy of Flight
A fused sternum with a “keel” provides the attachment points for the flight muscles.

7. THE BASICS OF FLIGHT
A flap is a flap
Flight feathers are asymmetrical to allow them to change shape during flight
A wing must allow air to pass through it on the up-stroke

8. Lift & dealing with drag
Lower air pressure above and higher pressure beneath wing creates lift
During flight, air currents coming off the trailing edge of the wing create eddies which cause drag
Eddy = DRAG
Lower pressure
Airflow
Wing cross-section
Higher Pressure
LIFT

9. DEALING WITH DRAG
Wing slotting
One way to reduce the drag caused by these eddies is to break them up into smaller eddies.
Primary feathers create smaller eddies = less drag

10. DEALING WITH DRAG
Ground effects
Flying very close (within a wing length) to a body of water allows the rippled surface to absorb the air currents coming off the trailing edge of the wing, reducing drag.

11. Powered Characterized by continuous flapping
THE BASICS OF FLIGHT
Powered
Characterized by continuous flapping
Results in a level course through the air
Examples: sandpipers, ducks, geese, rails and hummingbirds

12. Bounding THE BASICS OF FLIGHT
Birds flap in short bursts to gain altitude, and then descend with wings folded against the body
Bounding flight results in constant climbing and descending
Examples: warblers, vireos, small woodpeckers, orioles, robins and tanagers

13. Partially powered gliding
THE BASICS OF FLIGHT
Partially powered gliding
Partially powered gliding birds alternate between flapping their wings and holding them extended
Small hawks use flapping to fly between thermals
Examples: cranes, swallows, swifts, pelicans, and shearwaters

14. Ratio measures horizontal distance to vertical drop
THE BASICS OF FLIGHT
Gliding
Gliding birds keep their wings extended and ride rising currents of warm air to stay aloft. They flap only to regain altitude.
SAILPLANE 60:1
ALBATROSS 20:1
HAWK 10 to 13:1
MONARCH BUTTERFLY 3:1
Ratio measures horizontal distance to vertical drop

15. Route finding
Birds navigate by: visual landmarks, the sun, moon, stars, and routes learned from other birds
Birds also have an internal compass which is sensitive to the Earth’s magnetic field
Migrating birds will maintain a true compass heading
STARS
MAGNETIC NORTH
MOON
SUNRISE
WINDS
LANDSCAPE FEATURES
UV LIGHT
WEATHER
SMELLS
SOUND

16. Birds usually select the most efficient flight speeds.
How fast?
Birds usually select the most efficient flight speeds. 10 20 30 40
50 mph
28-50
COMMON LOON
32-46
OSPREY
30-44
BROAD-WINGED HAWK
28-40
GOLDEN PLOVER
SEMI-PALMATED PLOVER
22-32
BALTIMORE ORIOLE
22-30
BLACKPOLL WARBLER
15-23

17. How long?
Migrants using powered flight regularly cross stretches of open water like the Gulf of Mexico (500 miles)
Others flap continuously for as long as 70 hours
Examples: Ruby-throated hummingbird, Wood thrush and Blackpoll warbler

18. How far? NORTH AMERICAN MIGRATION FLYWAYS
Atlantic Flyways Mississippi Flyways
Central Flyways Pacific Flyways

19. How far?
7,000 miles
one way
Red Knot Flies from Argentina to Brazil, to the Delaware Bay, to the Arctic.

20. How far?
2,500 to 5,000 miles
one way
Blackpoll warbler Winter in South America, and fly to the Caribbean, and then to northern breeding grounds.

21. Some fly across the Gulf of Mexico. (500 miles nonstop)
How far?
Some fly across the Gulf of Mexico. (500 miles nonstop)
Hummingbirds Winter in Central America and fly as far north as Canada.

22. How far?
7,000 miles
one way
Blue-winged Teal Winters in South America, and breeds in northern plains

23. DAY OR NIGHT?
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

24. DAY OR NIGHT?
Nocturnal migrants
Many birds which use powered flight are nocturnal migrants. Why…?
Night flying helps birds avoid predators
Other benefits include calmer, more stable air

25. Fat is the currency of migration
Fat is the most important fuel for migration
Many species double their weight with fat fuel for migration
Typical Body Fat: PRE-MIGRATION
Shorebird
Songbird
Hawk
66%
70%
15%

26. Fat is the currency of migration
RED KNOT BODY FAT 3%
66%
PRE-MIGRATION (Brazil)
POST-MIGRATION (Delaware Bay)

27. Re-fueling stations are critical
When a Red Knot arrives at the Delaware Bay, in two weeks it must increase its body weight by 60% to complete the trip to its arctic feeding grounds. The additional weight must be in the form of fat…
A 175 lb man who wants to gain 105 lbs (60%) in two weeks would have to eat 46 Big Macs per day for 14 days…
…and turn it all into fat!

28. Birds rely on the same re-fueling stations
Stopover places provide abundant food for re-fueling needed by shorebirds to complete migration, as well as roosting places.
Bay of Fundy, ME
James Bay, Canada
Gray’s Harbor, WA
Platte River, NE
Delaware Bay, MD
San Francisco CA
Cheyenne Bottoms, KS
Copper River Delta, AK

29. The biggest threat to migration is habitat loss
Threats to migration
The biggest threat to migration is habitat loss
Loss of non-breeding ranges due to agriculture and seaside development
The destruction of the tropical and boreal forests
Habitat fragmentation

30. Everything in the world is connected to everything else
Migratory routes are the invisible lines of connection which show us how people, places, and wildlife depend on each other
Migration tells us about our physical and spiritual health