Biological mechanisms

• Annual rhythm.
• Innate behaviour pattern stimulated by environmental cues (shortened day length is the cue for preparation - candidates should explain that this is more reliable than factors such as temperature which may fluctuate; change in wind patterns is the cue for departure).
• Biological clock mechanisms - explained in terms of the responses
• Navigation methods - relevant to this bird, eg sun compasses, star patterns, Earth's magnetic field, possibly landmarks for northward journey. Explanation of the need for multiple methods of navigation required. Earth's movement with respect to the sun and the ability of the bird to compensate for this is explained.