From 1969 until today, researchers at Manomet in southeastern Massachusetts have banded birds every autumn from August 15 to November 15, from Monday through Friday, from dawn to dusk. Many bird species have been declining in abundance and migrating later (or in a few cases earlier) over this 39-year period.
In a recent paper in Biological Conservation, we demonstrate that if bird banders sampled fewer days per week, even as few as two days per week, the patterns of changing abundance and timing are still detectable over the 39-year period.
Our results demonstrate that the key to detecting long-term changes in abundance and timing of migration is to establish a simple and efficient sampling design that can be carried out over a long period of time.
You can read the full article here.