Abstract Crossbills of different average size in Scotland give different flight and/or excitement calls. Generally, crossbills that give a particular flight call also give a particular excitement call, thereby defining ‘call-types’. Here, different calls and their varieties are described for different sizes of crossbill (i.e. species). Also described are the different call-types of Common Crossbills Loxia curvirostra of varying average size (wing length and bill size). Using calls to identify crossbills is less subjective than trying to discern small differences in bill size, and the results of this study may help observers who record crossbill calls.
To read the issue in full, you can subscribe to BB here