Canon & Sigma?

[squishy]

If you can keep the shutter speed over 1/800sec, you should be able to handhold easily, it's reasonably lightweight for a 400mm. Slower than that and it it a little less certain, you probably can handhold for sharp shots down to about 1/400sec, but it would be less reliable and you'd lose a certain percentage of your shots to camera shake. I can't speak from experience with the 400 prime, but when I've experimented with my 100-400mm with the IS off, those are the kind of shutter speeds I had to aim for.
Try using your 150-500 handheld with the OS off (and shooting wide open), see how it is (and bare in mind the 400 will be noticeably lighter).

It's got a 'bad' minimum focussing distance of 3.5m, but for 99% of birds this would not be any issue at all (but if you want to use it for dragonflies you'll need extension tubes or something, cos it isn't close enough).

I'd probably recommend a monopod. Easier to carry, lighter and faster than a tripod

[glsammy]

Originally Posted by Sam_swfc123

Thank you for all your comments and advice, very helpful.

One last question for you all though.

The Canon 400mm f/5.6 is it a lens that i would be able to take around the woods and on walks by free hand or do i have to have a tripod with it?

Please could i have a bit of information about please? thank you that would be very helpful.

Regards,
Sam Winslow.

The easiest solution is to use a monopod. I never use a tripod with mine, but I do a monopod. With that you can shoot as slow as you like without any problems. The main advantage with the 400mm F5.6 is how easy it is to use hand-held, being very light in comparison with most others of similar reach.