The role of phenotypic signals and genetic quality in male-male competition in birds

Principal researcher: Magdalena Zagalska-Neubauer

Period: 2014-2017

One of the most important manifestations of animals life is their ability to communicate effectively with each other. Morphological, behavioural or physiological characteristics are signals sent by the sender toward the recipient via different, often complementary, communication channels: chemical, tactile, visual and acoustic. Regardless of which channel is used in a communication process, the essential intention of a sender is to modify behaviour of the signal’s recipient in a manner beneficial to himself, while the recipient is trying to evaluate the received information and achieve maximum benefit from the interaction. In many animal species, particularly birds, visual and acoustic signals play a crucial role in both mate choice and interactions between individuals of the same sex. Through visual and acoustic signals, territorial males inform neighbours and intruders about their quality, motivation to defend the territory, and/or social status. Sexually selected traits often signal quality or motivation and form specific ‘status badges’. Such signals underlie intra- and intersexual communication and are central to the signalling theory. The signalling theory, to which the project refers, proposes that plumage traits or song characteristics have evolved to signal individual quality and the ability of individuals to win agonistic encounters. It is also possible that some of these signals indicate genetic potential of individuals. In general, signalling dominance brings benefits to the signaller and the receiver, as intrasexual competition over limited resources like territory, food and mates is often intense. Thus, mechanisms that settle conflicts without physical aggression are expected to be favoured by selection. Costs, benefits, and resultant fitness trade-offs are thought to maintain reliable status badges as evolutionarily stable signals. The main goal of our project is to evaluate phenotypic signals and to assess their relationship with evolutionarily important genes in male-male competition in the chaffinch (Fringilla coelebs). This small passerine has plumage with conspicuous white wing epaulettes, which potentially serve as quality indicators. It has been shown that larger epaulettes correlate with more aggressive behaviour and it is possible that honestly indicate male quality. Quality assessment based on the size of male epaulettes is possible only when individuals are well visible and in sight. For medium and long distance communication males use also the acoustic communication channel. The repertoire of chaffinch songs ranges only from 1 to 6 types of songs (usually 2-3 types). Each song consists of a trill and an ending song flourish. It has been shown that males react more aggressively to a song containing a more complex trill, which may suggest that trill complexity indicates male quality. Therefore, we can expect that signalling of male quality in the chaffinch acts in two dimensions - acoustic and visual, and the information transmitted by these two channels of communication could be correlated with each other. We hypothesise that epaulettes and song in the chaffinch are reliable signals of quality in male-male interactions during thebreeding territory defence. It is believed that it is only multiple ornaments that reflect different aspects of individual quality and allow a more accurate assessment of quality. To determine the relationship between aggressive behaviour and quality in social signalling in male chaffinches, we will measure phenotypic characters, assess MHC (Major Histocompatibility Complex) genes polymorphism and parasite load. We expect that males with larger epaulettes and more complex song would be less infected with malaria-like parasites and show a higher MHC polymorphism