Animal Migration Flashcards
Define migration
Regular movement back and forth between two relatively distant locations by animals that use resources concentrated in the different sites
Orientation types (3)
Pilotage
Compass Orientation
True navigation
Pilotage?
Use of familiar landmarks to direct
Compass orientation?
Movement in a certain direction, without landmarks
True navigation
Orientation towards a specific fixed point regardless of landmark or direction (animal can find its way from anywhere)
Evolution of migration in Catharus thrushes
Both resident and migratory members - residency ancestral, migration evolved 3 times
Costs of migration (6)
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
How can energy reserves affect migration?
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
Benefits of migration (3)
Better feeding opportunities
Predation avoidance
Environment e.g. avoid harsh weather
Emlen’s Funnel? What does it measure?
Way to study migration in the lab - funnel with ink pad to measure direction of bird hops, pre-migratory restlessness
Cues for migration? (5)
Visual Olfactory Atmospheric pressure Sound Geomagnetism
Sun compass use?
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
Physiological altimeter?
Allows response to air pressure e.g. in homing pigeons
Use of infrasound?
Detection of sound frequencies below 10Hz - e.g. from waves breaking on a beach
Evidence for olfactory cue use?
Homing pigeons with anosmia have impaired homing abilities
Green turtles released upwind of Ascension island found it harder to locate
Magnetic compass as a cue?
Magnetoreceptors e.g. suggested in the beaks of homing pigeons, eyes of European robins
What does night migration use?
Star compass
Calibrated magnetic compass
Polarised light
Role of star compass?
Stellar cues allow orientation
Rotation of sky key - stationary = no direction
Rotation around Polaris important - changing this changed migration direction
Calibration of flight direction at night?
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
Polarised light use?
Animal retinas detect scattering of light - filters affecting this changes migration behaviour at night
Path integration (local map)
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
Evidence for a continental map?
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
