Is coverage needed of the same area (tetrads) every year?
No. For the more intensive method (Timed Tetrad Visits), the basic requirement for each tetrad covered is two 1-hour TTVs in one winter, and two 1-hour TTVs in one breeding season. Otherwise there would not be time to cover a large sample of different tetrads over the full survey period. However, Roving Records can be collected from any (or all) winter or breeding seasons.
