92 posted something on the 'Dumbed Down' thread that brought to mind a experimental study I read of some years back. It was conducted by Otto Kroenig, an Austrian animal psychologist in 1965. The results of the study were published in Der Spiegel in 1966 but I have not been able to find anything published directly by Kroenig himself. I read of the study on http://www.fee.org/the_freeman/detail/of-birds-and-men#axzz2ceHKsQ3e and its implications have stayed with me. The article goes into a little detail as to how and why the act of making the birds dependent on a supplied source of food caused a complete collapse of the colony. It's not very long and certainly worth the 5 minutes it takes to read it.