Usage and plasticity of sexually selected signals: the role of background noise individual learning and signal amplitude

To understand how animals communicate and how their signals evolved, we need to know what information their signals convey and the selective forces that have shaped them. A high proportion of animal communication research has been on vocal signals, with bird song one of the most useful models. Bird song is particularly interesting because, in addition to natural selection acting on sound transmission, it is also subject to sexual selection by female choice and male-male competition. However, it is often forgotten that bird song is a multifaceted behaviour, and one of the most important parameters for transmission, how loud the signal is, has been neglected, although it may have an important role in encoding information. To fill this crucial gap in our knowledge, we propose (1) to investigate whether birds are able to adjust the frequency characteristics of their songs to reduce interference from background noise, and whether such an adaptation is related to song learning, and (2) to determine whether song amplitude is an honest indicator of the current and/or past condition of signalling males. To investigate how adaptation to background noise is achieved, we will use great tits in a song learning experiment in which they will be exposed to different noise profiles. The topic of the information coded in signal amplitude will be addressed in experiments with breeding zebra finches. The results of the project will increase our knowledge of how the environment influences the evolution of sexually selected signals and how this is affected by individual learning processes. It will also help to shed light on which messages can be encoded in the amplitude of a sexually selected signal. In addition to this impact on theory, the proposed research also has applied potential: many habitats are affected by man-made noise and the world is becoming more and more noisy because of progressing urbanisation and increasing local and global traffic. It is therefore of great importance for conservation to find out how adaptable the communication systems of animals are and the extent to which a vocalising animal can cope with interference from noise.

The advertisement signals of sexually-displaying males are among the most widely studied phenomena in animal behaviour. In particular, many of our current advances in understanding animal communication and sexual selection derive from studies on bird song. The specific purpose of this research proposal is to investigate how sexually selected signals can be affected be environmental influences, how this is related to individual learning and, in addition, to determine the messages that can be encoded in the signal amplitude. Therefore we plan to investigate whether birds are able to adjust the frequency characteristics of their songs to reduce interference from background noise and whether such an adaptation is related to song learning, and (2) determine whether song amplitude is an honest indicator of current and/or past condition of signalling males. To investigate how adaptation to noise is achieved, we will use great tits in a song learning experiments in which they will be exposed to different noise profiles. The topic of information coding in signal amplitude will be addressed in experiments with zebra finches, in which we will test the influence of a male's food intake rate and the effect developmental stress experienced early in life. The results of the project will increase our knowledge of how the environment affects the evolution of sexually selected signals and how this is related to individual learning processes. It will also help to shed light on which messages can be encoded in the amplitude of a sexually selected signal. In addition to this impact on theory, the proposed research also has applied potential: many habitats are affected by anthropogenic noise and the noise levels in many areas are expected to raise dramatically in the near future. It is therefore of great importance for conservation to find out how adaptable the communication systems of animals are and the extent to which a vocalising animal can cope with interference from noise.