Most back gardens host the same handful of species year-round, plus a few seasonal visitors. Learning to recognise the regulars by silhouette and sound takes a few days of paying attention. After that, anything unusual stands out immediately.
The regulars
House sparrows are the small brown bickering birds that travel in loose groups. The males have a grey cap and a black bib; females are plainer. They are loud, communal, and almost never alone. If you see one sparrow, there are usually six more nearby.
Blue tits and great tits look similar at a glance — both small, blue and yellow. Great tits are bigger, with a black cap and a thick black stripe down the chest. Blue tits have a blue cap and no chest stripe. Both are acrobatic and not shy of feeders.
Robins are reliably present in European gardens, less so in North America. The orange-red breast is unmistakable; both sexes look alike. They are territorial and often the first bird singing in the morning.
Blackbirds are common, large, and confusingly named — only the males are black with a yellow eye-ring and bill. Females are dark brown. They forage on the ground, hopping a few steps and pausing to listen for worms.
Easy confusions
Wood pigeons and collared doves are both grey-pink and similar in size. Wood pigeons have a white patch on the neck and a heavier silhouette. Collared doves have a thin black collar and look slimmer. The call gives them away too — wood pigeons coo in five-note phrases, collared doves in three.
Dunnocks get mistaken for sparrows. They are about the same size and brownish, but the bill is thinner and pointed (sparrows have a thick seed-eater bill), and they creep along the ground rather than hopping in groups.
What to learn first
Sound matters more than sight. Most birds are heard before they are seen, and many are too small or too quick to identify visually. There are free apps that record a snippet and suggest a match — useful for learning, less useful in the long run when you want to do it yourself. Pick three or four species to learn each week and the soundtrack of the garden will start making sense.