It depends what you want to use the pictures for. Go to http://images.google.com and type in geese in the search box. You will find many pictures of geese (some flying in formation), but these pictures are not necessarily copyright-free. For personal use (not for displaying on the web), you are likely to have fair use rights to use them, but for commercial use or for wider distribution (such as displaying on the web), you are not
--Davi
If clip art is sufficient for your needs, you may be able to find something
in the Microsoft ClipArt library as well. Try typing "birds" and see
what comes up.