Quality is important.

Manual focussing is far too slow to focus on a flying bird. If your camera supports predictive AF, then this is the best mode for moving objects. 

Autofocus is generally faster with a DSLR than on a bridge or compact camera, and will be even better with a wide aperture telephoto lens. Unfortunately such fancy lenses are horrendously expensive. Often this combination of camera and lens is unwieldy and serious bird photographers tend to use a tripod, or at the very least a monopod to steady the camera. 

It is worth trying with whatever camera you have, but the odds are improved with the big lenses. 

Vince---it was a job getting this little chap flitting about, but got him in the end.  Have a look at Roy Jackson's bird photos; some of the best on the site here I think.

A longer focal lenght does seem to help the camera's focusing system, here using a 200mm lens with a 1.4TC.

Picture by Paul Hilton

Once again, a longer focal lenght  (here an effective 260mm on the Nikon D70) has helped the auto focus not to focus on the pier in the background.

Picture by Paul Hilton

Foxes viewed through the lavatory window!  Did this affect your work flow John? 

I think we would like to see a sample!

To be serious though, if you capture the cub or adult foxes, choose the one you like best and I bet it will be well worth seeing by us on POE.