Final answer:
The best method to monitor a population of swallows is tracking individuals at a central watering hole while using a camera trap is the appropriate method for monitoring a population of tortoises.
Step-by-step explanation:
For monitoring a population of swallows, the best method would be to track how many and which individuals use a central watering hole. This method allows for direct observation of the swallows' activity and provides accurate data on population size and behavior. On the other hand, for monitoring a population of tortoises, the most appropriate method would be to employ a camera trap in the middle of their habitat. This technique allows for continuous monitoring of the tortoises without causing disturbance or altering their natural behavior.