Context dependent signalling in birds

We all like very simple explanations for what we observe – and in fact, much of science is based on the principal of parsimony where the simplest explanation is considered the best. But nature is messy, it runs many different ‘experiments’ where the details matter, and all of this gets even more complicated when you deal with social groups where both cooperation and conflict are a regular part of life. In this talk, I use my own work looking at the evolution of complex social signals in two species of songbird to illustrate the role of context dependent social behavior in the evolution of signals. These examples show how social selection can generate diversity and how relatively simple interactions can generate complexity. The good news is that by digging into the details of the system, we can actually decompose this complexity and start to understand it. The first story I will talk about (briefly) is how variation in social contexts during male-male competition and variation in environments across time for female mate choice can influence the evolution of sexual signals in the lark bunting (Calamospiza melanocorys). This example is informative in that it shows how selection pressures across contexts can counteract long term selection and preserve variation in sexual signalling traits. The second story I will talk about (in more detail) is how variation in social structure can favour the evolution of multiple social signals in wintering birds – golden crowned sparrows (Zonotrichia melanocorys). In this example we start with a basic question about badges of status and discover complex social structure in wintering birds and that this social structure has a profound impact on the evolution of social signals.