Compare data gathered in different environments. How should data be collected to ensure a fair comparison? How do you ensure that the same bird doesn't get counted twice? Such questions should help pupils realise the importance of developing standard rules for data collection to ensure quality. A project repeated over several years might identify trends in local populations.
How can you estimate of the number of birds in a large flock?
* What is the average speed of swans and geese migrating here from Iceland with a tail-wind?