Bird Bird MigrationMigration

Why Why Migrate?Migrate?

Escape fromEscape from

-bad -bad weatherweather

-lack of food-lack of food

Major North American Flyways

IInsectivorous birds such as warblers nsectivorous birds such as warblers

Fruit (berry) eating birds suchFruit (berry) eating birds suchAs cedar waxwingsAs cedar waxwings

ExamplesExamples

Types of MigrationTypes of Migration

• Seasonal North/SouthSeasonal North/South– Primary patternPrimary pattern

• Elevational MigrationsElevational Migrations– Summer/winter shift from high Summer/winter shift from high

elevations to low elevationselevations to low elevations• LatitudinalLatitudinal

– Movement from interior areas to Movement from interior areas to shore areasshore areas

Western Tanager

Preparing Preparing for Migration for Migration

• MoltingMolting– New feather growth needed for New feather growth needed for

long migratory flightslong migratory flights• Putting on weightPutting on weight - Some birds can double their - Some birds can double their weight in a period of 2 – 3 weeks.weight in a period of 2 – 3 weeks.

Trigger for migrationTrigger for migration

• Day lengthDay length

-increase of day-length at the end of -increase of day-length at the end of

winter stimulates bird pituitary gland.winter stimulates bird pituitary gland.

-hormones produced trigger -hormones produced trigger accumulationaccumulation

of fat, migration, courtship and of fat, migration, courtship and mating,mating,

nesting and care of young. nesting and care of young.

Finding the wayFinding 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, theykeep on course knowing where it should be at a given time of day.

What if they cannot see?What if they cannot see?

Night navigation by the stars Night navigation by the stars – orient to the north starorient to the north star

Storms or cloudy weather Storms or cloudy weather – orient to the earth’s magnetic fieldorient to the earth’s magnetic field

2 Reproductive Strategies2 Reproductive Strategies1.1. AltricialAltricial

– – Babies are hatched naked and blindBabies are hatched naked and blind - Cannot fly, walk or find food- Cannot fly, walk or find food

- Few eggs are laid (2 – 3)- Few eggs are laid (2 – 3)- Parents invest much energy in care - Parents invest much energy in care -If young are preyed upon, the eggs -If young are preyed upon, the eggs

are easily replaced (short incubation are easily replaced (short incubation time)time)

- Examples are- Examples are robins, swallowsrobins, swallows wrens, hawkswrens, hawks

--Young are hatched covered with down feathersYoung are hatched covered with down feathers

-Many eggs are laid (6 – 15)-Many eggs are laid (6 – 15)

-Parents invest a lot of energy in -Parents invest a lot of energy in

producing many large eggsproducing many large eggs

-Young are well developed and can -Young are well developed and can

move and feed shortly after hatchingmove and feed shortly after hatching

-Difficult to replace if preyed upon-Difficult to replace if preyed upon

-Examples are-Examples are

ducks, geese,ducks, geese,

swans, chickensswans, chickens

2. Precocial2. Precocial