The bird's appearance is not particularly arresting; 16 centimetres long, brown body feathers and reddish brown tail feathers, a white breast. But the song! Already in 1555, Konrad Gesner, reported "and that no-one doubt, such [singing] comes from art." Not only scientists were inspired, several composers incorporated the music of Luscinia megarhynchos into their compositions; for instance, Ludwig van Beethoven in his 6th Symphony, Johann Strauss with the "Nightingale Polka" or Igor Strawinsky with the "Song of the Nightingale". The nightingale, "a small bird with a tremendous voice", as Germany's Nature Protection Society declares in its description of "Bird of the Year 1995". The Swiss Bird Protection Sanctuary in Sempach is somewhat more reserved (1). In "Birds of Switzerland" by Marcel Burkhardt and Hans Schmid (2) we learn that "Nightingales live secret lives and only draw attention to themselves by their singing."

Females and males sing during the day

The resonant singing is the research subject of Valentin Amrhein and Marc Naguib from the universities of Basle and Bielefeld, respectively. Both researchers have been investigating the behaviour of nightingales for many years and their emphasis is on the bird's means of communication. Now, together with Pius Korner of the ETH Zurich, whom Amrhein has known since his student days in Basle, the scientists have published an article on the subject in the renowned specialist magazine "Animal Behaviour" (3).

Valentin Amrhein (seated) fixing a coloured identity ring to a nightingale. large

"Not all nightingales sing at night" the three authors report. During the day both female and male run through their repertoire of 260 "verses", which usually mutate after a few seconds to the nightingale's well-known song. But during the night, some of the birds are silent. "During the night only those males who have no partner sing" the scientists say. Over a period of three years Amrhein, Korner and Naguib studied a colony of about 30 nightingales and examined their singing habits in the Petite Camargue Alsacienne, a region of France around 10 kilometres north of Basle. "The results of this study have delivered the first indications that the nightly singing serves to attract the female" they write in "Animal Behaviour", published by the Association for the Study of Animal Behaviour.

"Nightingale males return from their winter quarters in the south earlier than the females", explains Pius Korner. On their arrival the males occupy a space and begin to sing during the night. The scientists were able to observe this in 16 of the 18 pairs that consequently bred together.

Nightingale with a telemetric transmitter on its back. The transmitter is stuck to the feathers and makes individual identification possible. It falls off after two or three weeks. large

"But all singing males became silent once they had found a partner", says Korner "only 12 bachelors carried on with their trilling". Shortly before the eggs were laid acoustic activity increased and for about three nights, successful males also began to sing again. After that all fell silent again.

Invitation to an amorous caper?

Amrhein, Korner and Naguib asked themselves, "why this second phase of nightly singing?" and they came up with three propositions. It is possible that the male sings to induce the female to come to him, for a so-called "extrapair copulation". Or the male sings to warn off his rivals (who is also looking for an extrapair copulation). It is also possible that the male wants to impress his own partner with his singing and incite her to greater reproductive willingness. Perhaps females lay more or better eggs the more often their partners sing.

Genetic analysis is needed

Korner is sure that, "at the beginning of the season, the nightly song attracts the female." Why the male takes up his song again once the female has laid her eggs is not yet clear–it might have both intra- and inter-sexual meaning. It might be a tactic to animate the female as well as to see off competitors. In a further step, genetic examinations will carried out on the young. This will determine whether the second singing phase of the successful suitor actually led to an illicit coupling.