Where are all the Redstarts! (1 Viewer)

I went down to Exmoor two days ago birding in the horner water/cloutsham area, I also went there two weeks ago. In total I managed to see just one Redstart, whereas a few years back I would have seen many more birds.
I suppose they migrate to Africa (my bird book doesn't show the wintering areas), maybe they are dying down there - I've heard they are fairly liberal with their use of insecticides (mind you, I suppose we are pretty bad in this country too!), does anyone have any opinions on this subject?

Thanks

Indy

I've got 90% Redstarts and Yellow warblers at my local patch.(CT. U.S.A.)