Where have all the birds gone?

Last year there were so many birds which I took photos of nearly every day, but this year there have been virtually none for weeks.  Because this is only my second year I do not know if these kinds of fluctuations are normal, because the weather this Spring was totally different to last year.
The teal all left many weeks ago, but there are no red-shank, or plovers, or little egrets.  The only birds remaining are the gulls and a pair of oyster catchers and the resident pair of swans, plus an occasional mallard or two. One day I saw a little grebe, and on another I saw two.
Yesterday I was so pleased to see a greater crested grebe which spent some time feeding in the cut as the tide was going down. I found that Redwood makes a good hide because I can get on her when the bird is diving, and then be much closed for the photos.  Soon she will have windows and then I can just look out of them!  Once she is in her proper place I will be able to take photos out of my own windows again .. at present all I can see is the black side of Redwood.