Causes and consequences of song amplitude adjustmentin a territorial bird: a case study in nightingales

Vocal amplitude, one of the crucial factors for the exchange of acoustic signals, has been neglected instudies of animal communication, but recent studies on song variation in Common Nightingales Lusciniamegarhynchos have revealed new insights into its importance in the singing behavior of territorial birds. Innightingales song amplitude is not maximized per se, but is individually regulated according to the levelof masking background noise. Also, birds adjust their vocal intensity according to social variables, as inmale-male interactions. Moreover, during such interactions, males exploited the directionality of their songsto broadcast them in the direction of the intended receivers ensuring the most effective signal transmission.Studies of the development of this typical long-range signaling suggest that sound level is highly interrelatedwith overall developmental progression and learning, and thus should be viewed as an integral part of songontogeny. I conclude that song amplitude is a dynamic feature of the avian signal system, which is individuallyregulated according to the ecological demands of signal transmission and the social context of communication.

HENRIK BRUMM, An Acad Bras Cienc (2004) 76 (2)