1. Bird Migration

2. Why Migrate? Escape from -lack of food -bad weather
Major North American Flyways

3. Examples Insectivorous birds such as warblers
Fruit (berry) eating birds such
As cedar waxwings

4. Types of Migration Seasonal North/South Primary pattern
Elevational Migrations
Summer/winter shift from high elevations to low elevations
Latitudinal
Movement from interior areas to shore areas
Western Tanager

5. Preparing for Migration
Molting
New feather growth needed for long migratory flights
Putting on weight
- Some birds can double their
weight in a period of 2 – 3 weeks.

6. Trigger for migration
Day length
-increase of day-length at the end of
winter stimulates bird pituitary gland.
-hormones produced trigger accumulation
of fat, migration, courtship and mating,
nesting and care of young.

7. Finding the way Visual -Topographical landmarks such as
mountains, lakes, cities, rivers, etc.
-Familiar routes learned along with flock
Sense of time
-Allows them to navigate by sun-
azimuth orientation. Use the sun as a
compass. As it moves across the sky, they
keep on course knowing where it should
be at a given time of day.

8. What if they cannot see? Night navigation by the stars
orient to the north star
Storms or cloudy weather
orient to the earth’s magnetic field

9. 2 Reproductive Strategies
Altricial
– Babies are hatched naked and blind
- Cannot fly, walk or find food
- Few eggs are laid (2 – 3)
- Parents invest much energy in care
-If young are preyed upon, the eggs
are easily replaced (short incubation
time)
- Examples are
robins, swallows
wrens, hawks

10. 2. Precocial -Young are hatched covered with down feathers
-Many eggs are laid (6 – 15)
-Parents invest a lot of energy in
producing many large eggs
-Young are well developed and can
move and feed shortly after hatching
-Difficult to replace if preyed upon
-Examples are
ducks, geese,
swans, chickens