A full national survey was undertaken in 2006, repeating the survey last done in 1994. This was an important survey for Hampshire which has a significant population of Dartford Warblers. The survey involved at least two visits to every 1-km square where there had been Dartford Warblers in recent years, plus visits to some additional, randomly-chosen, squares.
Preliminary results suggests that Dartford Warbler numbers were well down on 2005, and perhaps that the total was down on the 1994 Hampshire population. Many observers have suggested that the relatively cold weather in late winter and early spring of 2006 may have impacted Dartford Warblers quite hard.
The 2006 survey and others were summarised in a paper in the 2010 Hampshire Bird Report.