AV or TV

SO here is the question, AV mode or TV mode ?
I am by no means class myself as an expert everything I say here is my opinion and based on my experience.
One golden rule for me and I hope all other wildlife photographers:
Never ever disturb or upset any wildlife by getting to close just to get a photograph.

Back off there will always be another day !!

I always thought that birds and wildlife in general needed to be photographed with a fairly high shutter speed to capture the detail at its best and to freeze any possible motion blur, and this is true to a certain extent, thus I first started out by shooting in TV mode however I was always disappointed with most of my results, I could never get the entire subject tac sharp, this was due to the lack of Depth Of Field (DOF) it wasn't until my friend said that he uses AV mode all the time  (except for Birds In Flight (BIF) never goes over iso200 that I thought I would give it a try, I don't say that I agree whole heartedly with using AV but it definitely produces some good results as it gives you full control over the all important DOF.
The goal for me is to try to get the whole bird sharp from the tip of its beak to the tip of its tail, and capture as much detail as possible, sounds easy doesn't it, but its surprisingly difficult and a technically challenging thing to get right, some people say as long as you get the eye sharp the rest doesn't matter, well that isn't good enough for me, I want to see the entire subject sharp as possible.
Birds are very rarely still for long, occasionally you may get one that perches for a while but rule of thumb is they are constantly flitting about looking for food or keeping out of the way of predators, some live in bushes and reeds and are rarely seen like this distant shot of a Bittern.

  Canon 5dmk4 700mm F7.1 1/1250 iso800

This was taken at Stodmarsh NNR from the David Feast hide, I had been to the Marsh hide and bumped into a guy I had seen on several occasions, he had told me that he had seen the Bittern from this hide regularly for the last few weeks, anyway it didn't show at the Marsh hide.
As I was on my way back to the car I popped into the DF hide and there skulking along at the back of the pool was the Bittern, it was the first time I had seen one so had to take a few shots of it.
Its always ironic and normally turns out that its just a matter of being in the right place at the right time.
Anyway I digress, my preference is AV mode, this gives me full control over how much of the subject is in acceptable focus.
So here is the trade off, ideally you want a sufficient DOF to get the entire subject sharp whilst having a shutter speed as high as possible given the current lighting conditions to freeze the subjects movement.
DOF is a funny old thing which I will cover in a future blog.
 I don't consider myself proficient enough as yet to use manual mode, and I don't want to miss a shot because I am still fiddling with shutter speed and aperture whilst a bird disappears off into the distance.
Using a support is important, nothing compensates for a bean bag or a sturdy tripod this can allow you to shoot at really low shutter speeds and still obtain a tac sharp image.

So for the time being I will continue to use AV mode.