With a camera that is!
These were taken at the Don Edwards nature preserve in Alviso.
This is a lot harder than I thought. More so than small birds. Butterflys in general have a very sketchy flight pattern. This is made more difficult if there is one or a few of the specie.
The trick I have found is to follow their erratic flight(imagine nervous waving of camera/lens).
Then be ready to smooth out the panning when they do a very short float/glide.
I bumped the ISO to 200, to keep shutter speeds very high (1/4000) @f5.6
I have had better luck w/Monarchs, but they are more numerous, better odds I guess.
This was just one Swallowtail, patrolling for a mate.
I used my 1DMkII in AiServo mode for the focusing to track them.
I don’t think single focus would work well enough.
I only used the 200mm so they aren’t close enough. I forgot to bring the teleconverter
But a longer lens would be a challenge keeping them in the frame.
Here are three images. They are cropped a lot, but at least they are pretty sharp
The key to any wildlife photography is knowing your subject. Observe before you start shooting and look for the patterns and habits. Something will be revealed that will tell you the best opportunity.