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Jason, 210 mm. will not give satisfactory results for bird photography. In a pair of binoculars, it would be the equivalent of 4x. Everyone I know who watches birds through binoculars uses at least 8x to 10x.
If he is on a budget, he might look at the Sigma DL or APO Macro 70-300 f4.0-5.6. There are two versions and grades. The APO is more expensive, but still very affordable, and gives better results due to its apochromatic design. That said, it has noticeable edge weakness at 300 mm., unless you shoot it at f16. Center sharpness is okay at 300 mm. If your father is using autofocus on birds, then perhaps center sharpness is what he needs. He will be more satisfied with 300 mm than with 200 (but be sure he understands shooting at 1/focal length). In any case, the Sigma is probably your best bet for the money. It has a nice macro mode. There is a comparable model from Tamron, but many consider it not to be as good.
Here's a couple of photos taken with the Sigma APO, 300 mm., wide open (f5.6):
http://pug.komkon.org/04oct/mopti.html
http://pug.komkon.org/03mar/djnmsqsn.html
Here's another taken in macro mode:
http://pug.komkon.org/03may/buttrfly.html
Joe
