Abstract
The rate of urbanization world-wide is alarming with respect to its environmental impact and conservation. At the same time it provides a natural laboratory with an ongoing experiment of an unprecedented scale. Urban habitat confronts animals, including humans, with evolutionarily speaking novel selection pressures, such as a dramatically different acoustic environment. Some species thrive in urban settings, others perish, but we often have no clue how or why. The great tit is an urban survivor, despite its dependence on acoustic signals for territory defence and mate attraction. We have previously shown they have adjusted their songs in pitch: the use of low-pitched notes is negatively correlated to the presence of loud, low-pitched traffic noise. This is true at the individual level within a single population and at the population level across Europe in ten independent city-forest comparisons. Knowledge about the underlying behavioural mechanism for this species may lead to insight into why others are less successful breeders in a noisy environment. In the proposed project, we will take an experimental approach to test whether adult birds have indeed a short-term acoustic flexibility to adjust to local noise conditions. We plan to test the impact of masking noise on the acoustic response of territorial males and to test the capacity and constraints to converge to new song types by using playbacks. The results may also generate new insights with respect to the song learning and crystallization process in general. A second component concerns the assessment of fitness consequences of unavoidable, masking noise. We will collaborate with established research groups with long-term data on reproduction and survival of two great tit study populations. Again we will take an experimental approach to avoid typical confounding factors in naturally noisy habitat in cities or along highways. We will measure the impact of experimentally increased noise levels on singing and other territorial behaviour, and assess reproductive success, extra-pair paternity, and survival or territory tenure length. The impact of masking noise and adjusted song types on female choice will be tested using a standard Skinner box set-up with two pecking keys which trigger song playback in the laboratory. We have extensive experience with several species in this set-up, and, although great tits have been used in operant conditioning experiments, this would be the first time for this well-studied model species.
Netherlands