References: Thank you to the following:
1.
Gen Comp Endocrinol. 2008 Aug;158(1):10-9. Epub 2008 May 29.
2. http://www.pbs.org/wgbh/nova/sciencenow/3214/03-brain.html
3.
Images are from Google Images : http://images.google.com/
4. Bird sounds are from : http://www.enature.com/birding/audio.asp