Some species can be a bit tricky to tell apart or even see at all. Here are some tips...
Swallows, House Martins, and Swifts
Look at wing and tail shape and how it flies.
Chiffchaff
It sings its name!
Cuckoo
It sings its name too!
Blackthorn and Hawthorn
Blackthorn flowers before it leaves, and hawthorne leaves before it flowers.