SEEN - SE European Bird Migration Network
Development in the cage data elaboration
Przemysław Busse
Bird Migration Research Station, University of Gdansk, Poland

Assumptions and the basics of elaboration of data collected using the orientation cages were listed and discussed in first papers presenting new design of orientation cage (Busse 1995, Busse and Trocinska 1999). The standard accepted was to show individual bird behaviour as pointers demonstrating direction and “a power” that gives an idea about concentration of recorded scratches. To show a population pattern it was used summing up individual pointers and presenting its distribution in 60 six-degree sectors. Obtained pictures showed distributions in detail, but they were very difficult to analyse and it was hard to convince people not acquainted to such pictures (strange “asterisks” of broad and narrow pointers). There were some trials how to simplify these patterns but results were of limited value as the pointer type presentation force to look at detail elements not the more general pattern. The next trial gone in direction of grouping the data into bigger sectors. The first association was to put individual pointers into eight sectors, exactly as data were collected, and present the result as a polygon that could show general patterns. However, such pictures were too generalised and not useful enough. Finally, grouping the individual pointers into 16 sectors was chosen and the pattern is shown as the polygon. This possibility is available in the new version of ORIENT program.
This method of presentation gives very good visualization of headings, possibility to calculate average azimuths for bird groups and testing of agreement of headings of different groups. Number of good examples will be presented as well as arguments for standard use of “reversed” patterns in the data presentation.
Created by Pronetix 2006