Make a cylinder or something in the shape of a nest, and use the compound scatter object to place any number of different sized twigs on the outside surface of the cylinder-type object. Having several different-shaped twigs scattered over it will give you the variation you need, and using the compound object's tweakable parameters you'll be able to create the randomness that you need without having to place every twig
(you could actually do the same with pflow, and it would be much easier to do....but I don't have time to write the full explanation other than to say: used instanced geometry as your particle shape, and position object as your starting point and all your particles should have a speed of zero)