Does substrate quality influence take-off decisions in Common Starlings?

1. An instrumented perch was used to measure the reaction forces during tak e-off of starlings from perches of three thicknesses. There was no signific ant decrease in reaction force with decreasing perch thickness; however, ov er the range of perch sizes there was a 10-fold decrease in safety factor a nd a 400-fold increase in the energy of deflection of the thinnest perch. 2. The implications of these results are that birds do not change their tak e-off strategy when faced with perches of variable thickness and that, as a result, leaps from thin perches are very much less efficient than those fr om thicker perches. Birds appear not to adjust their leaping behaviour to m inimize the risk of substrate failure during take-offs.