For photos of birds, wildlife, and scenery I recommend you buy two lenses. Those 18-200mm lenses and such are just junk. You should buy a good quality zoom lens and a good wide angle.
I don't know your price range, are you talking $ or £?.. One of the best lenses to start off on if you are talking $ (I think you are) would be the 70-200mm f/4 L IS.
http://the-digital-picture.com/Reviews/Canon-EF-70-200mm-f-4.0-L-IS-USM-Lens-Review.aspx
If it pushes your budget then drop down to the Non-IS version..
http://the-digital-picture.com/Reviews/Canon-EF-70-200mm-f-4.0-L-USM-Lens-Review.aspx
Both are very high quality, superb lenses. They make great general wildlife lenses (they are the equivalent of 112-320mm on the crop sensor) and also make fine portrait lenses.
The money you have left over should be spent on a wide angle lens. You will not have much change left over to be honest so I recommend the 18-55mm f/3.5-5.6 IS lens..
http://the-digital-picture.com/Reviews/Canon-EF-S-18-55mm-f-3.5-5.6-IS-Lens-Review.aspx
This is a surprisingly good lens and produces good results. It will also double up as a good walkabout lens until you save some money up and maybe buy the wonderful 17-55mm f/2.8.
http://the-digital-picture.com/Reviews/Canon-EF-S-17-55mm-f-2.8-IS-USM-Lens-Review.aspx
or the 10-22mm
http://the-digital-picture.com/Reviews/Canon-EF-S-10-22mm-f-3.5-4.5-USM-Lens-Review.aspx
As far as straps go, the 50D will come with one in the box, but I highly recommend the OpTech Pro strap (about £15)..
http://chili-pix.ch/shop/images/_MG_4940.jpg
VERY comfortable strap and great if you have a heavy lens and battery grip attached.
Forget about screen protectors, not necessary.
Fish-eye lens?, couldn't tell you, overpriced and unnecessary if you ask me.
I advise to buy a battery grip for the 50D, it helps balance the camera with a longer lens, gives you an extra shutter in portrait mode, better battery life, and you can pretend you are holding a 1Ds. I have mine attached to my 40D 100% of the time.
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