[Orgmode] How to set a set of headlines (at the same level)

[Charles Cave]

I would like to see a feature to sort the set of branches into alphabetical 
order.
At the moment I have to manually move the subtrees up and done.

Here is an example:

Before sorting

* New words
** bird 
A bird can fly
*** sub topic
blah blah
** fred
A Fred is a frog
** cat
A cat is an animal
** aviary
Where birds are kept


After sorting...

* New words
** aviary
Where birds are kept
** bird 
A bird can fly
*** sub topic
blah blah (sub topics could appear in the tree)
** cat
A cat is an animal
** fred
A Fred is a frog


The sorting algorithm needs to call  org-move-subtree-up  and 
org-move-subtree-down 
depending on the comparison of adjacent headings.

How difficult would it be to add this functionality? The command should work
on a region.  I want to create an org-mode file of vocabulary. I note that it is
possible to sort table rows so that is a possible work around for me.

Charles