Seasonality / periodicity
Birds can be seen as ultimate robots.
A book called the ‘Dictionary of Birds’ in 1985
has a figure where the chaffinch activity was documented.
Rhythm occurs because of the pineal gland. It is not the light sensor, like it is in reptiles. The pineal gland produces melatonin. Production of melatonin has a daily rhythm.
Red, orange and yellow light is effective at getting their testes larger (Benoit 1950).
Types of light regimes:
Males grew their testes best at a 3 to 3 rhythm.
Starling with different testes throughout the year:
Old world warblers breed in central Europe and over winter in the Congo. Fly over the rock of Gibraltar and then turn left and fly to their destination in the Congo. When they return they fly strait north. Use an inc blotter on birds feet and try to find what direction birds are flying in. Birds kept in a cage in Germany orient themselves in the same direction as all the other wild birds. Direction of orientation is endogenous. Birds trapped in a cage in Germany when they should turn left, show unique directional preferences. Same with when birds should fly north. AFTER Gwinner and Wiltschko 1978, 1980).
We know a lot about orientation in birds, but we know nothing of navigation.
By Rob Nelson
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