@natashag: Hovering over your icon on the upper right side* will open a menu.
Choose account settings. About two-thirds of the way down the Account Settings page you can change your license. There are CC options and No license (all rights reserved copyright).
@natashag - Your copyrights cover three distinct things: sound files, photos, and the actual observation. You can change any/all of them by going to your profile tab and selecting “Edit account settings & profile”. Scroll down to “Licensing” and choose what you’re comfortable with.
Just a quick note to say that legally, any content accessed under a CC license is so available in perpetuity.
There is little point changing observations or images published as CC to a closed license. Unless you significantly modify these, the originals will always be available under a CC license.