There was an error published in J. Exp. Biol. 216, 1819-1826.
In supplementary material Table S1, the data for kestrel are actually for sparrowhawk. The correct file is now available at http://jeb.biologists.org/content/216/10/1819/suppl/DC1. The authors apologise for any inconvenience that this error may have caused but assure readers that it does not affect the results or conclusions of the paper, or supplementary material Fig. S1.