Fluctuating asymmetry and feather growth bars as biomarkers to assess habitat quality of shade coffee farming for avian diversity conservation

Shade coffee farming has been promoted as a means for combining sustainable use of forests and biodiversity conservation. With the increasing intensification of coffee production, methods of habitat quality assessment using measuring body conditions of individual birds may provide a more direct evidence of the contemporary quality of shade coffee farming for avian biodiversity before any demographic changes can be noticed. With this study, we applied fluctuating asymmetry on tarsi length and ptilochronology (relative growth bar width) to determine the habitat quality of shade coffee farming. The extend of fluctuating asymmetry in tarsus length showed no difference between shade coffee farming and natural forest in any of the studied avian functional guilds (forest specialist and generalist, as well as obligate and opportunistic insectivores). Similarly, no difference was found in growth bar width in any of these guilds with the exception of forest specialist birds which had narrower gro...