You mean the Time Machine, battery, time/date, wireless etc. icons?
I don't know how to make them smaller, but if you right click on them, you can change what you see. For example the battery can show the icon only, and how much time is left on it in minutes or percentage - you can remove that part to free up some space. Ditto the date and time formats.
I'm sorry I can't help any more than that, but someone may be able to.