How do you do this correctly?

[Joaquin Barbará]

I was at the local park today where a little old lady had set up a bird feeder and there were a bunch of Black-Capped Chikadees feeding on it. I decided that since I had rented a D3s for the weekend I was going to use it as a machine gun and try to get some Chikadees in flight.
I set up my camera in front of the bird feeder and focused on the edge of the feeder since most of the birds were coming almost paralel to my sensor.
I cranked up the ISO to mantain a SS above 2000 and set my f/stop to 8.0 (thinking that would increase my DOF).
When I saw the bird start to approach the feeder I would start shooting in continous mode. I ended up with bunch of good poses but most were OOF.
When I got home I used an online DOF calculator and for
Nikon D3s
Focal Length 420 mm (Nikon 300mm f/4 + 1.4 TC)
f/8
Distance 10 feet
I get a whooping DOF of 0.07 feet or almost ONE WHOLE inch. Half of it in front and half of it behind my point of focus.
It is now clear to me that this way I am going to end up with very few keepers. Is there an easier way of doing this?
Shorter focal length with remote trigger?

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[David Stephens]

You answered your own question with your DOF calculation. You need to go to single-point AF and track the birds in and off the feeder, in this case. Use the feeder to prefocus, but you'll need to catch the bird as it comes in or lifts off. A feeder is great for practice, but we'll be more impressed with natural looking setups. Getting lift-off is easier than landing for these small fast birds.

In your example, you've focused on the front/right side of the feeder and the chickadee is approaching from behind that plain. Hence, your OOF.

[Diane Miller]

And in addition, most DOF calculators I've used have given me a value that is far too optimistic in my estimation.

[Sidharth Kodikal]

Joaquin, here's another method for consideration.

If possible,
1) try to control where the bird will come in to land (e.g. by taping off most of the feeder except for a sliver). The more spots you give the bird to land on the harder it gets for you.
2) try to control the birds flight path by giving it a take-off perch close to the feeding station
3) with your gear parallel to the planned flight path, manually focus on a spot either close to the feeder opening where the bird is meant to land or close to the take off perch for, well, a take off shot
4) fire off as the bird takes flight.

Consider purchasing Alan Murphy's ebooks (if you haven't already) that describe such setups in great detail.

PS: for tiny, speedy birds, I'd push for an SS over 1/2500 (ideally 1/4000 if possible)

[Miguel Palaviccini]

Sidharth nailed it with his suggestions.