Bird Photography Equipment - Lenses

When I first started photographing birds I had a Canon 100-400mm F4.5-5.6 EF L IS the original push pull zoom version and whilst it did reap some good results I found that my sensor was always getting dusty, I later found out that this was a common complaint with this lens.
I also always found that I was using it at the 400mm end of the zoom, so I decided to ditch the 100-400mm for a 400mm prime.
I found one and duly purchased it Canon 400mm F5.6 EF L USM, this lens does not have any IS and is light as a feather and in good light a solid birding lens.
However having seen the results my friend was getting using a 500mm prime I wanted one !
After a lot of searching I found one on Ebay for a good price, also it had just had a service prior to the sale just so that the seller knew it was all working.
So this is now my weapon of choice, yes its heavy but it is worth lugging it around to get some spectacular results.

Kingfisher taken using Canon 5dmk4 700mm F14 1\200th ISO800

Sometimes to get professional quality captures you need to spend some money on good equipment.

Stonechat taken using Canon 5dmk3 700mm F9 1\640th ISO320

Both the above shots were taken using my 500mm F4 L IS with the addition of the Canon 1.4x Extender mk3 to give me a 700mm focal length with very little loss in quality and only one stop of light, its a very good trade off, I use this a lot.