Create channels for each site then you will be able to track the clicks. (when creating a new ads(generate code) make a new channel (at bottom) name it so you will under stand e.g. "footer banner sitename"
Go to your Adsense account. Select AdSense Setup Select Channels Select Adsense for content, URL channels Select Add new URL channels Enter the url of the site you want to follow You can also track the individual ad blocks in a site by giving them custom channels. Read more in the Guide to Using Channels on the Channels page!