Can measures for modelling bird flight be replaced by measures taken easily on live birds and museum skins?

ABSTRACT Usually, some measurements are taken from birds caught for ringing, for example to differentiate between species, subspecies or sexes, or to obtain a measure of body size or energy stores. However, the ecomorphological interpretation of standard measures of the flight apparatus is often difficult, because flight models need parameters that are not among the standard measures taken by field ornithologists. Therefore we evaluated on dead European Robins Erithacus rubecula and Eurasian Blackcaps Sylvia atricapilla how well a suite of measures that can be easily taken on a live bird is correlated with the aerodynamically relevant parameters wingspan, wing area, wing chord, aspect ratio and wing pointedness. We found that wing chord is well correlated with the length of secondary 2, wingspan with the length of the primary that forms the wingtip of the spread wing, and wing area with the length of the longest primary. Aspect ratio and wing pointedness were poorly correlated with alternative measures. Compound measures did not significantly improve these relationships, while some multivariate models did. From the limited data set of this study, it seems that aerodynamically relevant parameters can be substituted to a certain extent by measures that can easily be taken from live birds or museum skins. This may serve intraspecific studies in which data from live birds or museum skins are collected with the aim of interpreting their flight performance in a correlative way.