Animal Migration

Question 1

Define migration

Answer 1

Regular movement back and forth between two relatively distant locations by animals that use resources concentrated in the different sites

Question 2

Orientation types (3)

Answer 2

Pilotage
Compass Orientation
True navigation

Question 3

Pilotage?

Answer 3

Use of familiar landmarks to direct

Question 4

Compass orientation?

Answer 4

Movement in a certain direction, without landmarks

Question 5

True navigation

Answer 5

Orientation towards a specific fixed point regardless of landmark or direction (animal can find its way from anywhere)

Question 6

Evolution of migration in Catharus thrushes

Answer 6

Both resident and migratory members - residency ancestral, migration evolved 3 times

Question 7

Costs of migration (6)

Answer 7

Extra weight for energy reserves
Temporary atrophy of reproductive organs
Increase in muscle contraction efficiency
Altered metabolism to fat storage
Risk of death on trip
Encounter multiple habitats; must be adapted to them all

Question 8

How can energy reserves affect migration?

Answer 8

Can influence the route e.g. red eyed vireo

Low energy migration results in land route from Alabama to central America, high energy = crosses gulf of Mexico

Question 9

Benefits of migration (3)

Answer 9

Better feeding opportunities
Predation avoidance
Environment e.g. avoid harsh weather

Question 10

Emlen’s Funnel? What does it measure?

Answer 10

Way to study migration in the lab - funnel with ink pad to measure direction of bird hops, pre-migratory restlessness

Question 11

Cues for migration? (5)

Answer 11

Visual
Olfactory
Atmospheric pressure
Sound 
Geomagnetism

Question 12

Sun compass use?

Answer 12

Animals e.g. starlings can control for the movement of the sun depending on time of day/season = innate time-compensated sun compass, linked to their endogenous clock

Question 13

Physiological altimeter?

Answer 13

Allows response to air pressure e.g. in homing pigeons

Question 14

Use of infrasound?

Answer 14

Detection of sound frequencies below 10Hz - e.g. from waves breaking on a beach

Question 15

Evidence for olfactory cue use?

Answer 15

Homing pigeons with anosmia have impaired homing abilities

Green turtles released upwind of Ascension island found it harder to locate

Question 16

Magnetic compass as a cue?

Answer 16

Magnetoreceptors e.g. suggested in the beaks of homing pigeons, eyes of European robins

Question 17

What does night migration use?

Answer 17

Star compass
Calibrated magnetic compass
Polarised light

Question 18

Role of star compass?

Answer 18

Stellar cues allow orientation
Rotation of sky key - stationary = no direction
Rotation around Polaris important - changing this changed migration direction

Question 19

Calibration of flight direction at night?

Answer 19

E.g. in thrushes, use of cues at twilight to adapt day compass for night travelling
If this is interfered with one night, it can be fixed the next with normal cues

Question 20

Polarised light use?

Answer 20

Animal retinas detect scattering of light - filters affecting this changes migration behaviour at night

Question 21

Path integration (local map)

Answer 21

A mental map that uses landmarks to navigate a local environment e.g. desert ants, which forage randomly outside and still pick the shortage route back

Question 22

Evidence for a continental map?

Answer 22

White-crowned sparrows translocated from west to east USA initially started in their usual compass direction and corrected this upon hitting the coast.
Juveniles did not show this - experience is needed