If I instantiate an FBO without binding a rendering buffer or a texture to it, what happens when I draw to it, nothing?

Do I need to associate a rendering target (renderbuffer or texture) to have an FBO do anything? What I'm trying to do is precache some buffers and then merge them later, but that doesn't seem to work at all.

Ideally I'd like to do something like

glBindFramebufferOES(GL_FRAMEBUFFER_OES, fbo1);
// Draw some stuff to fbo1
glBindFramebufferOES(GL_FRAMEBUFFER_OES, fbo2);
// Draw some stuff to fbo2
// ...
// ...
// glRenderFbo(fbo1); -- Not a func
// Set blending, etc. etc.
// glRenderFbo(fbo2); -- Not a func