I wrote this review about 'Trees' in the same series; in my opinion it hold true for the whole series.
In my opinion it is little short of a scandal that the Clue series of books from OUP are out of print.
They are simply THE most wonderful resource for primary aged children to use in the identification of a range of British flora and fauna.
As a teacher I used them throughout 30 years of my career, and children and staff loved them. As a parent I bought them for my child, and they are still used by my grandchildren.
If OUP had an ounce (or a gram) of commercial sense, they would revise and reissue them, and extend the series as much as possible. They would be an excellence resource within the National Curriculum for primary science.
Clue published volumes relating to Birds, Flowers, Tracks and Signs, Insects, Trees, Freshwater Animals, and Seashore Animals. There may be more for all I know; if there were and I knew where to find them, I'd buy them!!