<ul>
<?php
wp_list_pages('depth=1&title_li=0&sort_column=menu_order');
if(current_user_can('read_private_pages')) :
?>
<li><a href="<?php echo get_permalink(10); ?>">For Authors only</a></li>
<?php endif; ?>
</ul>

http://www.wprecipes.com/how-to-add-privates-pages-in-navigation-menus

Add privates pages in navigation menus

wordpress

PHP