Animal Migration
What is migration?
Migration:
 Seasonal back and
forth journeys between
two sites
Migrant vs. Resident
Which animals migrate?
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Mammals
Birds
Amphibians
Reptiles
Fish
Insects
Why do animals migrate?
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Opportunism – exploitation of
ephemeral/seasonal resources
Cost benefit ratio
Types of Migration
1.
2.
3.
4.
5.
Latitudinal
Altitudinal
Reproductive
Seasonal
Irruptive
Types of Migration
Obligate annual migration
1. 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?
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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
Can estimate general population trends from number of
migrating individuals counted
Photo by B. Webb
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
 Signal from transmitter
to satellite
 Location downloaded
from satellite
Radio telemetry
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
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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
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80% of breeding bird spp. in N. America
Complex annual life cycle
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breeding areas (2-3 mths)
migratory pathways (2-3 mths)
wintering areas (6-7 mths)
Declines in many spp.
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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
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Breeding Bird Survey
species-specific studies
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population estimates on breeding and
wintering grounds
Western meadowlark
Painted bunting
Population trends: 1996-2003
Cerulean warbler
Linkages between annual stages
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American redstart
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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
350,000 Thompson’s
gazelles
200,000 plains zebra
Mammal migration: Serengenti
Dangers: Serengeti migration
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Predation
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Land and water
Rinderpest
Human
population
growth
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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 Migration
Pacific 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
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International cooperation (Partners in Flight)
Incentives for developing countries to
protect migratory wildlife and habitat
Public education: consumer choices