decrease in sunlight change in precipitation increase in food source change in wind direction
I gave my students this multiple choice question: What abiotic factor would most likely signal a population of birds that it is time to migrate from north to south?

Only one answer is correct among these 4 choices:
- decrease in sunlight
- change in precipitation
- increase in food source
- change in wind direction

Could you tell me which one is correct?

decrease in sunlight