context: In the tropics there is little variation in the length of day throughout the year, and it is always warm enough for a food supply, but altitudinal migration occurs in some tropical birds. There is evidence that this enables the migrants to obtain more of their preferred foods such as fruits.
question: সারা বছর ধরে দিনের দৈর্ঘ্যের মধ্যে সামান্য পার্থক্য কোথায়?
answers: In the tropics