[freiston]

I believe that Err1 signifies contact problems - Nigel's pencil eraser tip sounds good - you might want to hold the camera body/lens with the contacts pointing downwards to reduce the risk of eraser dust/debris falling into the hardware.

I had a Tamron 70-300 that made a 'bad' noise and then gave the Err99. I can't be sure, but I think I might have changed lenses without switching the camera off, immediately before the problem manifested. I replaced it with another Tamron 70-300 (F4-5.6 Di LD Macro 1:2) and have had no problems.

I have recently bought the Sigma 150-500 OS - the image stabilisation does help with hand-held shots, which is a good thing because the lens needs a lot of light. It is a lot sharper than the Tamron and does not suffer from purple fringing like the Tamron does - but it did cost over five times as much as the Tamron.

The Sigma is big and heavy and not a low light performer - so I only use it when I 'plan' to - otherwise the Tamron goes out with me for convenience and versatility.

I'm not sure what you mean by the Canon 200mm or 300mm Sigma that you refer to - they are both 'prime' lenses (fixed focal length instead of zoom), and they don't come cheap. Without more detail as to the lenses and price range that you're looking at, and also without knowing if it will be your only lens or if you want to use the lens for photographing other than the swans, I find it hard to suggest something.