%0 Journal Article
%T Vocal Communication in Androgynous Territorial Defense by Migratory Birds
%A Eugene S. Morton
%A Bridget J. M. Stutchbury
%J ISRN Zoology
%D 2012
%R 10.5402/2012/729307
%X Many temperate zone breeding birds spend their non-breeding period in the tropics where they defend individual territories. Unlike tropical birds that use song for breeding and non-breeding territorial defense, vocal defense differs strikingly between breeding and non-breeding territories in migrants. Song, restricted to males, is used during defense of breeding territories but callnotes are used to defend non-breeding territories. To explain why callnotes and not songs predominate in the non-breeding context, we present an empirical model based upon predictions from motivational/structural rules, ranging theory and latitudinal differences in extra-pair mating systems. Due to sex role divergence during breeding that favors singing in males, but not females, females may be unable to range male song. Ranging requires a signal to be in both the sender and receiverĄ¯s repertoire to allow the distance between them to be assessed (ranged). Non-breeding territories of migrants are defended by both males and females as exclusive individual (androgynous) territories. Ranging Theory predicts callnotes, being shared by both males and females can, in turn, be ranged by both so are effective in androgynous territoriality. Where songs are used for non-breeding territorial defense both sexes sing, supporting the evolutionary significance of shared vocalizations in androgynous territorial defense. 1. Introduction A continuing challenge in evolution is to identify the sources of selection acting on signal structure in vocal communication. Research has recently shifted from an emphasis on information transfer, wherein the senderĄ¯s goals determine signal structure, to the receiverĄ¯s goals (e.g., [1]). Under the receiver control model, receiver assessment of signals feeds back to the sender by influencing what the senderĄ¯s signals have accomplished [2¨C4]. Assessment insures that signals are honest and allows us to identify results of sexual conflict (Sensu [5]). Here, we provide an example of how signal assessment can produce seasonal signal structure changes in the same individuals in the context of territorial defense. Many migrant birds are territorial in temperate-zone-breeding areas and resume territorial behavior when they reach nonbreeding areas. They are, in essence, territorial throughout the year but breeding and nonbreeding territories are widely separated, often thousands of kilometers apart, in space as well as in time [6]. There are major changes in territorial behavior between breeding and nonbreeding periods that affect the context of communication. While
%U http://www.hindawi.com/journals/isrn.zoology/2012/729307/