Hi Stratman!
This is a great picture. The baby birds with their mouths wide open - I can hear their squealing!!
The purple fringing is really not noticeable to me. I've seen much, MUCH worse. I looked at the large version of your picture. I don't have that lens, so I can't tell you if it's just from that lens.
I get it horribly when I use the Vivitar 2X macro focusing teleconverter:
I didn't do it with this picture because I didn't notice it until after I'd finished uploading the picture, but the Power Retouche tools (Photoshop plugins) have an excellent purple fringe remover. I'll have to redo this picture and show you the difference. Don't know if there are any other tools like this around...