A dark, stocky warbler, the Cetti's warbler is most likely to be heard, rather than seen - listen out for its bubbling song among willow, marsh and nettles.

Bittersweet is a nightshade, so is toxic; its bright red berries may be tempting, but can cause serious illness. Found in hedgerows and gardens, it has purple flowers with yellow stamens.

The muntjac deer was introduced into the UK from China in the 20th century. It has gained a stronghold in southeast England, where it can cause damage to our woods through browsing.

The oak marble gall wasp produces brown, marble-shaped growths, or 'galls', on oak twigs. Inside the gall, the larvae of the wasp feed on the host tissues, but cause little damage.

A scarce and declining bird, the tree sparrow can be spotted on farmland and in woodlands; it is not an urban bird in the UK. It has a brown cap and black cheek-spots, unlike the similar house…

The common dandelion is a most familiar flower: counting down the 'clock', while blowing the fluffy seeds from its head, is a favourite childhood game. Dandelions are an important early…

The sanderling scampers about the waves looking for marine crustaceans, fish and even jellyfish to eat. It visits the UK in winter from its Arctic breeding grounds, but can also be seen as it…

The common spangle gall wasp produces a small, disc-shaped growth, or 'gall', on the undersides of oak leaves. Inside the gall, the larvae of the wasp feed on the host tissues, but cause…