A stocky, little sandpiper, the knot can be spotted in estuaries from August onwards, migrating here from the Arctic where it breeds. Look out for it probing the muddy sand with its specialised…

The tiny, brown-and-white sand martin is a common summer visitor to the UK, nesting in colonies on rivers, lakes and flooded gravel pits. It returns to Africa in winter.

The common polypody is a hardy fern of damp, shady places in woodlands. It also makes a good garden fern. It has ladder-like, leathery foliage with pimply undersides - these spots are the spores…

Found in ponds and marshes, the fragile look of the Common water-measurer belies its fierce nature. A predator of small insects, it uses the vibrations of the water's surface to locate its…

The eerie, 'cur-lee' call of the curlew is a recognisable sound of wet grasslands, moorlands, farmland and coasts. Its long, downcurved bill is an unmistakeable feature and perfect for…

Sometimes called 'Wild spinach', Sea beet can be cooked and eaten. It grows wild on shingle beaches, cliffs and bare ground near to the sea, as well as in saltmarshes.

Often spotted in large flocks, the fieldfare is an attractive thrush. It is a winter visitor, enjoying the feast of seasonal berries the UK's hedgerows, woodlands and parks have to offer.

Escaped or intentionally freed from fur farms in the 1960s, the American mink is now well established in the UK. Its carnivorous nature is a threat to our native water vole and seabird populations…

The eel is famous for both its slippery nature and its mammoth migration from its freshwater home to the Sargasso Sea where it breeds. It has suffered dramatic declines and is a protected species…