B&B Magnetoreception

Question 1

What is bird ringing?

Answer 1

Birds caught in mist nets
Against dark background find it hard to see net
Bird ringer extracts bird
Numbered ring attached to leg
Unique sequence - address, numbers,letters

Question 2

What is remote sensing?

Answer 2

Radio tags (find location, temperature, heart rate)
Geo-locators = light and time recorders (Satellite tags, accelerometers, immersion/depth loggers)

Question 3

Size of trackers are dependent on a bird’s body mass. Geologgers are some of the smallest trackers, what are some of the largest?

Answer 3

Satellite GPS

Cellular GPS

Question 4

Why are tags attached to the Caledonian crow?

Answer 4

Tool users
Video, GPS and visual tags
Filming between birds legs
Film tool use

Question 5

What did fitting tracking devices to the red necked phalarope show?

Answer 5

Amazing migration
Fly north to iceland - greenland - south of unites states then to peru
In spring this is reversed

Question 6

What is an irruptive migrating species?

Answer 6

eg Waxwings
Winter visitors to Britain
Only in some winters
When their main food source (berries) has run out further north
Indicates true migration, not simple landmark navigation

eg short eared owls
Main food source is Voles
When it runs out, wonder further south

Question 7

How do animals orientate using landmarks?

Answer 7

Squirrels use landmarks to remember where they are storing food
birds migrating

Question 8

How do animals orientate by following their parents?

Answer 8

Bewick's swans
Individual face markings
Follow parents for first year or two
Including winter migration
Experience first migration by following first route eg learning landmarks

Question 9

Cuckoos
Don’t meet their own parents
Lay egg into Reed Warbler nest
Feed cuckoo chick
Don’t migrate with reed warbler parents and never met real parents
How do they and others carry out true navigation?

Answer 9

Piloting = orientation in relation to landmarks
Compass orientation = flying at a certain angle to an external reference (eg earth’s magnetic field), non -specific goal
Goal orientation
Navigation (map + compass = true navigation)

Question 10

Some inexperienced birds show directional preferences which change over time. Name one bird that does this.

Answer 10

Garden Warblers

Believe there are genetic influences

Question 11

Describe the Emlen funnel

Answer 11

Temporarily held in cage at night
Direction at which they try to escape reveals their current directional flight preference
Ink pads - ink dots when try to escape
Defining the vector = quantify flight preferences

Question 12

What is the starling displacement experiment?

Answer 12

Starlings migrated to the netherlands
Pausing there
Capture them and displace them several km to south
Ringing them
Recorded areas birds were found
Adult starlings = reversed displacement by flying back to wintering areas. Experienced migrators. Displacement able to be reversed
Juveniles = carried on in same migartion orientation
Juvelines just carru on orientation
Adults had a goal orientation - ontogony

Question 13

Describe the vertebrate eye structure

Answer 13

Standard
Cornea, fovea, lens, pupil, iris, retina
Refraction/focusing by both cornea and lens
The fovea is an area of high visual activity
Birds can have more than one fovea
With a visual streak imaging the horizon

Question 14

Describe light receptor cells

Answer 14

Contain folded membranes layered with visual pigments to trap light from a narrow angle
Visual pigments absorb light energy
There are 10 billion rhodopsin molecules per photoreceptor
Crytochromes = dispersed across retina. Ability to detect earth’s magnetic field
Rods detect contrast = low light conditions
Cones detect colour = bright light conditions
Birds have single and double cones (colour determination), pigmented oil droplets (act as colour filters)

Question 15

What are the 2 main proposed mechanisms by which animals can detect the earth’s magnetic field?

Answer 15

Magnetite
Fe3O4 crystals in head
Surrounded by dense nerve endings
As birds move head, exerts small forces on crystals
Crystals surrounded by nerves, pull of magnetic field can be perceives by the birds

Radical pair mechanism
Light entering birds eye is causing displacement of an electron from one molecule to another
The original molecules has 2 e-, the 2 e- are entangled
Behaviour of 1 influences the other
When the light knocks 1 e- onto other molecule, those 2 e- are far apart but still entangled so behaviour influences each other
Sensitive to external forces eg magnetic field
Quantum phenomenon
Located in retina of right eye
Triggers crytochrome processes at blue end of spectrum
It could well be integrated with birds visual perception
Could be perceiving on top of visual field bands of light and dark

Question 16

How do foxes use the earths magnetic field to hunt?

Answer 16

Almost always jumped North east
Use alignment of magnetic field with direction of sound
Crytochrome

Question 17

How do animals use compasses?

Answer 17

Magnetic compass
Visual compass - position of stars in sky. Polaris is constant - fixed point
Sun compass - rises in east and sets in west. Clock + date + azimuth is latitude and longitude

Question 18

As sunlight enters the atmosphere, starts striking small particles like water droplets. If the light is reflected and scattered at 90 degrees from the incident sunlight - it is scattered in a single plane. What is this known as?

Answer 18

Plane polarisation
If it hit molecule and carries straight on = non polarised
If it hits a smaller angle, it is partly polarised
Results in pattern of polarised light in the sky that animals can see

Question 19

How are many animals able to perceive polarisation of light?

Answer 19

By aligning their photo receptors in the same plane
Results in a band of polarised light of sky at right angles to position of the sun
Position of the band varies with time of day, season, latitude and longitude
Useful for orientation and navigation even when sun is behind clouds

Question 20

How do birds use their sense of smell to know where they are

Answer 20

Storm petrel - sensitive to dimethyl sulphide. This is the smell phytoplankton give off when they are being grazed by zooplankton. Homing in on patches of dimethyl sulphide, they can zone in on their prey

Turkey vulture - sensitive to ketones. This is the smell rotting meat gives off

Question 21

Why is the Barn owl a highly effective hunter?

Answer 21

The owl’s face “mask” funnels sound towards the two ears
Fringe leading edge of wing feathers allows them to fly silently so wing beats don’t interfere with hearing
Right ear is higher than left ear. Can detect diff in amplitude. Diff time of arrival in both ears. - interaural time diff
Phase differences of ear pressure and diff in sound frequencies will vary depending of which direction the sound is coming from.