Look out for the swift-like shape of the hobby as it darts over heathlands and wetlands in summer. They are keen hunters, chasing and catching fast-flying dragonflies and small birds on the wing…

The ptarmigan is a master of disguise - matching its Highland surroundings perfectly by turning snow-white in winter and rock-grey in summer. It is confined to the mountains of Scotland, so is…

The Sitka spruce was introduced into the UK from North America in the 19th century. It has been widely planted as a forestry tree; look for classic needle-like leaves and pale brown, domed cones…

Introduced from Japan in the 19th century, Japanese knotweed is now an invasive non-native plant of many riverbanks, waste grounds and roadside verges, where it prevents native species from…

These non-native limpets arrived from America in the 19th century and are now widespread in the UK. They form stacks and have a specially adapted shell which, when flipped upside down, looks like…

Introduced into the UK in the 19th century, the diminutive little owl can now be seen along hedgerows, on farmland and in parkland across England and Wales. It often perches on a pole or rock,…

The Arctic tern is famed for its aggression towards any that would disturb its nest - it will dive-bomb intruders with its sharp beak. Large, noisy colonies can be found on the Farne Islands and…