WANTED: data on flock size of migrant birds departing from stopover sites

Andrew Berdahl, a postdoc at the Santa Fe Institute (USA), works on social animal behaviour, particularly in the context on migration. He is working with a physicist to make a more general version of a migration timing model that he originally developed for fish migration in a social context. It makes some specific predictions on group size distributions in migratory animals, especially ones that leave from common stop-over sites. He has been looking for some empirical data on group size distributions in migratory birds, but without much success. Could anyone point out literature data, or actually havs such data themselves? He is also interested in collaborations. Please reply to Andrew Berdahl [berdahl@santafe.edu] or myself  [barbara.helm@glasgow.ac.uk]