Lesson 16: Animal Travels + + Compass Flashcards
a compass
a system that helps animals maintain orientation
when does an animal show orientation
when it faces or travels a particular direction
sun compass of the european starling
starlings are daytime migrants and were hypothesized to use a sun compass
example of how a sun compass works
- first imagine the drawing of a compass being flat on the ground
- next, imaging that you are standing in the center of it
- now imaging that it is sunrise so the sun is in the east
- if you turn to face the sun, you will be looking east
- if you want to go north for example, you just need to turn 90 degrees to your left
basic sun conventions
- sun rises at 6 AM in the east and sets at 6 PM in the west
- we will assume that we’re in the northern hemisphere, so the sun moves through the southern sky at about 15 degrees per hour
order of sun appearing in the sky for the northern hemisphere
6 am - east
9 am - southeast
noon - south
3 pm - southwest
6 pm - west
sun compass of the european starling experiment
- the study apparatus was an outdoor arena with a moveable outer ring of food bins
- birds were trained to find food in the SW bin no matter which physical bin was in that location (controlled for visual cues)
- then birds were CLOCKSHIFTED by placing them indoors under artificial light, with the lights coming on in the morning at a shifted time so the “sun: rose for the birds at a different time than the actual sun outside
ex: normal is 6 am - 6pm
shifted: 3 am - 3pm
-if the birds were finding direction with a sun compass then clockshifted birds should make predictable mistakes about where the southwest bin was
-BECAUSE they would not know the correct time, so would not know where the sun really was in the sky
- lights in the lab on at 3AM and off at 3PM. bird tested at 9AM real time outside arena
Q: what time would the bird think it was when taken outside?What is bird time
Q:What direction would the bird think the sun was at
Q: How would it turn to reach the SW bin?
Q: Where would that actually take the bird?
A: It would have been awake for 6 hours so it would think it was awake for 6 hours after sunrise or 12 noon
A: It thinks it is actually 12 noon, so it would think the sun would be south
A: it would turn 45 degrees to its right
A: At 9AM the sun is actually in the SE so a 45 degree turn to the right would take it south
start compass of the Indigo Bunting
- Indigo buntings are night-flying migrants an were hypothesized to use star patterns as a compass
migratory restlessness
in aviaries in captivity, the buntings became very active in spring and fall when they were supposed to migrate. Moreover, in fall, the birds seemed to move to the south sides of their cages, and in spring, they moved to the north sides of the cages
