Stop to observe a pigeon (Columba livia) while walking in a square or along a street and you will see that Moves head rhythmically back and fortheven rather quickly. This rhythmic movement of the head is known as “head bobbing“, precisely “swinging head” in English, and is used to stabilize the field of vision while the bird walks. In reality, however, the pigeon only moves its head forward, then it remains motionless while the body also moves forward: the head does not actively move back! It seems to us that it is going backwards because it is the movement of the entire body forward that deceives us. You will also notice the same movement when observing a hen in the farmyard, a dove in the garden or a seagull by the sea; differently, this oscillation is absent in birds of prey such as the hawk or the buzzard and in insectivorous birds that eat in flight such as swallows. It is not simply a mechanical oscillatory movement as happens with our arms when we walk fast, but it serves to maintain the stable gaze even when the body is in motion. Allows many birds to see better and focus on objects: the faster the pace, the faster the swing pace.
How pigeon head bobbing works
The movement of the head of the pigeon and other birds has two phases: one of pushing and one of stopping. In the push phase the head moves rapidly forward, then it doesn’t go backbut remains immobile and stable during the forward movement of the rest of the body. In this way, the retina is more stable and the images are clearer. In several studies, pigeons were filmed while walking, running and flying and the images, broken down into single frames, were analyzed revealing that: the movement is clearly visible, particularly during walking, it is synchronized with that of the legs and has a frequency around 3-8 Hz also as a function of the speed itself. The head moves forward with each step so that it can remain stable as the rest of the body advances. It’s sort of optokinetic reflex, that is, a mechanism that coordinates eye movements with the movement of the surrounding environment to obtain clear vision. It also serves to compensate for the lateral position and the poor mobility of the eyes of the pigeon and other birds.
Which birds move their heads back and forth and what is it for
The movement of the head, stabilizing the visual field, helps in finding food on land. The position of the eyes and the structure of the retina determine head bobbing: for example, birds of prey that have the eyes facing forward and hunting in flight, they do not swing their heads. The same goes for Pelicans because they have very mobile eyes. Even the stride length It influences head bobbing, in fact, birds that hop or take small steps do not bob their heads.
Groups of birds that are more closely related from an evolutionary point of view display similar behaviors. In fact, in general, all species belonging to the same family or order show the same behavior. Ducks with webbed feet, like ducks, flamingos or cormorants, do not bob their heads either in water or on land. An exception is represented by black-headed gull (Chroicocephalus ridibundus), which has an oscillating movement of the head while searching for food in the mud, but not when walking on dry land or swimming.
