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The language of birds: 2. Calls

Besides singing, birds call. The chaffinch, in addition to its song, has nine different calls. They are the flight call, social call, aggressive call, injury call, three different courtship calls and three different alarm calls.

Chaffinch (Fringilla coelebs) (22K)

Chaffinch Fringilla coelebs. Chaffinches have nine different calls

The flight call ("tupe") is given by a bird intending to take flight and causes other chaffinches, usually in the caller's flock, to prepare for flight and to fly, for the call coordinates the activities of the flock. In spring a special use of the flight call by females seeking mates, attracts males to them.

The chaffinch's social call (the familiar "pink") is given by a bird temporarily separated from its flock (out of the breeding season) or its mate (during the breeding season). The same call may be used by a bird wishing to rally other chaffinches to help the caller mob an owl and successfully get it to move on. Thirdly, the social call is given when danger immediately threatens - when a hawk is approaching. The response it evokes is a dive for cover. Lastly, the social call is used aggressively as when one bird attacks another in a winter flock because it is too near to the caller.

The injury call (a squeak) is given by a bird who has been injured in fighting, and also (presumably) by a bird being grabbed by a predator. This "cry of pain" is likely to convey a sense of immediate danger; furthermore it is possible that such a sudden and intense shriek might startle an inexperienced predator into letting go.

Of the three alarm calls the "tew", alarm is given only by recently fledged birds and evokes escape behaviour. The "seee" alarm call and the "huit" alarm call are given only by cocks and only in the nesting season. The " seee" call is usually reserved for the sudden appearance of a hawk; the "huit" is sounded when the danger is less immediate. Both serve to alert other adult chaffinches and the latter call also silences nestlings. (The stonechat Saxicola torquata, incidentally, appears to employ its "whit" call mainly or even exclusively to stop young giving begging calls; and the older the nestling the more frequent the call since the parental effort expended in rearing them has been greater. )

Two of the courtship calls, "kseep" and "tchirp" are given by cock chaffinches to facilitate pair formation and the third courtship call ("seep") is an indication by a female that she is ready to copulate.

The vocabulary of adult chaffinches has been set out in detail because it indicates the level of sophistication achieved in just one species' sound communication system. In addition, two different begging notes are used by nestling and by fledgling chaffinches respectively.

I am going to discuss one or two of these calls in more detail. Firstly, alarm calls: calls associated with fear or danger. When a bird spots a potential enemy it may give an alarm call and those within earshot are at least alerted, and may at once take evasive action. The bird is sounding the alarm, giving a warning cry. Imagine a flock of waders on a mud flat. At any one point in time, several birds will have their heads up while the rest are probing the ooze for food. One of these spots a peregrine falcon Falco peregrinus, gives its alarm call, and in an instant all have their heads up and are ready to take appropriate action. A directly comparable situation with a small flock of tits feeding on the ground at the edge of a wood can be imagined as a sparrowhawk Accipiter nisus suddenly appears.

As with a bird in song, the raiser of the alarm runs the risk of drawing the attention of a predator to itself, except that now the enemy is actually in earshot, being the cause of the alarm. The risk to the alarm raiser is thus greater than the risk to the singer. Why then does the caller call? Only because, presumably, the balance of advantage lies with so doing, otherwise natural selection would hardly have given rise to alarm raising as a piece of behaviour. But what possible advantage could there be to outweigh the tell-tale disadvantage? This question has puzzled behavioural theorists for a long time, and has given rise to intense debate and at least seven theories. I will mention only two.

Suppose you are a member of a gregarious species whose strategy in the presence of an enemy is to "freeze" and hope in that way to escape detection. If you are the first to spot the danger and you do not call, then your flock-mates, who have not seen the enemy, will continue moving about and will give your position away as well as their own. Thus you call so that they do not attract the enemy to where you all are.

Alternatively, you may belong to a ground-feeding species that, when threatened, flies into a tree where it is more difficult to be captured. If you are again the first one to notice the danger and fly up on your own, you become the odd bird out, and predators tend to go for the singleton. You draw to yourself individual attention. If you call and the others fly with you you stand no greater chance of dying than they. It is a form of the safety in numbers argument. In both these cases you are warning the others, but for a selfish reason - and that is consistent with the concept of natural selection.

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