Why do you require such detailed data rather than just trail summaries?

Some monitors collect only trail summaries, that is, total eggs/nestlings/fledglings summed across all of the nests that they monitor, rather than nest-by-nest data. The reason why we need detailed data is complex, but here is an example that might help explain.

Imagine that you have 12 apple trees in your yard producing a total sum of 120 apples. If each of the 12 trees had about 10 apples, you might conclude that it was a very bad year, but that all of your trees were healthy. If all 120 apples were on one tree, then you would undoubtedly come to a different conclusion—perhaps hypothesizing that something was killing off your other trees. Summary data for an entire orchard (or trail) would not allow us to make this distinction and yet it is a distinction that is critically important for managing the future of the orchard.

If we are to become good predictors of, say, bluebird population trends into the future, we need to know how many pairs are reproducing successfully, what their clutch sizes are, how much they vary from one individual or year to the next, and how the number of pairs fluctuates over time. For any study of nest survival, we must have detailed data on each individual nest attempt.