Reading bird language: alarm calls and behaviour as clues

Besides their song, many songbirds have various calls: soft contact calls so as not to lose each other in the group, begging calls of the young and alarm calls when there is danger. Alarm calls often differ depending on the type of danger. With a perched enemy, such as a cat in a bush or an owl during the day, many birds call loudly, harshly and repeatedly and even gather around the enemy. This behaviour is called “mobbing”.

With danger from the air, such as a hunting bird of prey, you often hear short, high, thin calls that are hard to locate instead. This way a bird warns the others without revealing to the hunter where it is itself. Many birds also react to the alarm calls of other species, and squirrels and other mammals listen in as well.

Because each bird only reacts when the danger is close enough, alarm spreads like a wave. When a fox walks through the woods, the unrest moves with it. An alarm that moves therefore suggests a walking animal or person; an alarm that stays in one place for a long time often suggests a perched predator.

You can only recognise alarm if you know what “normal” sounds like. That is why the most important step is to choose a regular observation spot – in the garden, in the park or at the woodland edge – and sit there quietly again and again. Listen to how it sounds when everything is calm: relaxed song, occasional contact calls, the rustling of birds feeding on the ground.

Then watch for changes: does it suddenly go quiet? Do several birds fly up in a hurry at the same time? Are there harsh call series? Are many birds looking in the same direction? Often it is not a single call but the overall picture that counts. A single loud call can also be a squabble over food or a territorial fight.

A notebook helps enormously. Write down when the alarm began, where, what it sounded like and where it moved – and what you saw afterwards. Over time you will recognise patterns typical of your spot.

One of the most important insights when listening is uncomfortable: most of the time you are the trigger yourself. When you walk along a path, the alarm runs ahead of you and warns all the animals around. That is why noisy groups see so few animals in the woods.

When you arrive at your spot, notice how far this unrest reaches and how long it takes for the birds to settle again. If you walk more slowly, more quietly and not straight towards birds, the disturbance zone gets smaller. That is good not only for your observations but also for the animals, which spend less energy fleeing.

Jon Young popularised this reading of “bird language” in his book “What the Robin Knows”. What remains important: every interpretation is a guess that you test through your own observation. Bird-call apps can help with identification but do not replace listening in context.

Listening itself is harmless, but it can harm birds if done wrongly. Played bird calls (“playback”) can seriously disturb birds in the breeding season, because they suspect a rival in their territory. In protected areas this is often prohibited. Refrain from it and check local rules.

Do not go to nests either to see how the parents react. Repeated disturbance can make birds abandon their brood. If you hear an alarm, check from a distance with binoculars instead of walking over. That way the trigger – perhaps an owl at its roost – is also left undisturbed.

Sit at your spot regularly for 20 to 30 minutes over several weeks, ideally at similar times of day. The first minutes after arriving are usually restless; the real observing starts after that. Feel free to close your eyes now and then and try to assign each call to a direction.

Good species for beginners are conspicuous ones found in many European gardens and woods that give loud warnings, such as blackbirds and jays. But you do not need to be able to identify species to recognise alarm. With children this can become a game: who hears first that something is changing, and which direction does the unrest point to?