Animal Migration

What is migration?Migration: Seasonal back and forth journeys between two sites

Migrant vs. Resident

Which animals migrate?

Mammals Birds Amphibians Reptiles Fish Insects

Why do animals migrate?Why do animals migrate?

Opportunism – exploitation of ephemeral/seasonal resources

Cost benefit ratio

Types of Migration1. Latitudinal2. Altitudinal3. Reproductive4. Seasonal5. Irruptive

Types of MigrationObligate annual migration1. Latitudinal (north-south)

Short distance (within a continent) Some birds, bats, and whales

Long distance (between continents) Many species of songbirds, shorebirds,

waterfowl, hawks Some bats and whales

2. Elevational Movement up and down mountain slopes Related to weather (especially snow depth) and

food conditions deer, elk, Mountain Goats, Spotted Owls, some

songbirds

How do animals migrate?How do animals migrate?

Magnetic field Landmarks Alignment of

stars in night sky

Olfactory cues Combination

How do we know where animals go?

Direct observation Ex. Broad-tailed

hawk

Photo by B. Webb

Photo by B. Webb

Can estimate general population trends from number of migrating individuals counted

How do we know where animals go?

Capture, mark, recapture

How do we know where animals go?

Radar, radio & satellite telemetry Radar detection of neotropical migrant

birds

Trans Gulf-migrants leaving

How do we know where animals go?

Radar, radio & satellite telemetry Satellite telemetry Radio

telemetry

Signal from transmitter to satellite Location downloaded from satellite

Peregrine Falcon migration routes based on satellite transmitter data

Swainson’s Hawk migration routes based on satellite transmitter data

How do we know where animals go?

Intrinsic markers Stable isotopes Elements vary

in number of neutrons – C, N, H, O, S building blocks

Bird Migration

Over 5 billion land birds of 187 species migrate between Europe and Asia to Africa

Over 5 billion land birds of over 200 species migrate between North America and the New World tropics

75% of 650 bird species that nest in N. America migrate

Neotropical migrant birds

80% of breeding bird spp. in N. America

Complex annual life cycle breeding areas (2-3 mths)

migratory pathways (2-3 mths)

wintering areas (6-7 mths)

Declines in many spp. Pattern

Neotropical Migrant Bird Conservation

Many species declining Loss of multiple

habitats: Breeding Migration stopover

sites Wintering

3 ranges used by the Blackpoll Warbler each year

Neotropical Migrant Bird Conservation

Loss and fragmentation of winter habitat (tropical forest):

slash and burn agriculture pasture land for livestock production

commercial and illegal logging

How declines have been measured

Breeding Bird Survey species-specific studies

population estimates on breeding and wintering grounds

Western meadowlark Painted bunting Cerulean warblerPopulation trends: 1996-2003

Linkages between annual stages

American redstart link condition on wintering grounds to breeding

success Stable isotope analyses: ratios of C13:C12 High quality winter habitat (coastal

mangroves and lowland forests): wetter and C13 depleted

Birds from high quality winter habitat earlier on breeding grounds earlier breeding = more

chicks fledged

1.3 million wildebeest

200,000 plains zebra

350,000 Thompson’s gazelles

Mammal migration: Serengenti

Dangers: Serengeti Dangers: Serengeti migrationmigration

Predation Land and water

Rinderpest Human

population growth Land conversion Poaching esp.

resident animals

Sea Turtle Migration

Juveniles hatch on shore and migrate to the open ocean

After years in the open sea, juvenile turtles move to specific coastal feeding grounds

Young loggerhead sea turtles in the North Atlantic cover more than 9,000 miles before returning to the North American coast!

Adult turtles migrate between specific feeding areas and then back to nesting beaches

Juvenile Loggerhead Migration

Orientation during migration A variety of navigational cues are used Must stay in North Atlantic Gyre for several years to grow and develop Detect subtle differences in the earth’s magnetic fields to use as navigational markers

Adult Green Turtle Migration

Adult Green Turtles captured by fishermen at feeding grounds off coast of Nicaragua and branded Some turtles escaped after boat capsized at FL Keys Several months later same turtles recaptured in same area in Nicaragua Turtles use a magnetic compass and have map sense

Whale MigrationPacific Gray Whales • Longest known migration for any mammal: 10,000-12,000 miles annually!• Raise calves in nurseries (lagoons) of Baja California• Migrate to feed in the cold arctic seas• Nearshore migration route allows for easy observation, but harassment by whale-watching boats may be pushing whales off shore

Butterfly Migration

Monarch Butterflies • Fly up to 3,000 miles each way• Return to the same winter roosts, often to the exact same trees • Preferred conditions found in oyamel fir forests, which occur in a small area of mountain tops in central Mexico

Conservation Strategies International cooperation (Partners in Flight) Incentives for developing countries to

protect migratory wildlife and habitat Public education: consumer choices