Which Focus Mode to use for Wildlife?

[sm4him]

^THAT. READ the manual. More than once.
It can be boring, but it really IS very helpful.

I don't have a D7100 either; I use a D7000, but I *think* that particular setting is the same in both. Go to Shooting Menu (in Menu, the section with the camera icon), scroll down to "ISO sensitivity settings." Choose that and you'll see at the top, "ISO sensitivity" and some value. Set that to 100. Under it you'll see "Auto ISO sensitivity control" and it will likely be "off"--select ON instead and you're good to go. Like A said, it could be slightly different for the D7100.

Thanks... Its exactly the same on the d7100...

Soo i can set my aperture and shutter to whatever i want anf then the iso would change to compensate exposure... Is that how it works?

Basically. Just be aware that if you're at f/8 or 9, 1/1600 shutter speed at sunrise, shooting a heron flying along the bank, auto-ISO isn't going to save you. Take a test shot or two at your chosen settings, under the lighting conditions you have, and see what kind of ISO values it's giving you.
Generally speaking, I *like* to shoot birds at about f/8, 1/1000 and auto-ISO, because I know my camera and lens and know that's my best "go to" settings. But I also know, generally, whether my lighting conditions are going to allow for that--I'd PREFER to avoid all my photos being ISO 3200, if I can help it. So if I already know the lighting isn't great, I might open the aperture some--or if I know it's really, really bright, I might go on up to 1/2000.

For me, basically what auto-ISO does is gives me the flexibility to move straight from shooting into the blue sky at a bird in flight, to panning over to a shady, wooded section to catch an osprey landing in a tree without worrying about whether the exposure is going to be okay.

 

[Aloicious]

Basically. Just be aware that if you're at f/8 or 9, 1/1600 shutter speed at sunrise, shooting a heron flying along the bank, auto-ISO isn't going to save you. Take a test shot or two at your chosen settings, under the lighting conditions you have, and see what kind of ISO values it's giving you.
Generally speaking, I *like* to shoot birds at about f/8, 1/1000 and auto-ISO, because I know my camera and lens and know that's my best "go to" settings. But I also know, generally, whether my lighting conditions are going to allow for that--I'd PREFER to avoid all my photos being ISO 3200, if I can help it. So if I already know the lighting isn't great, I might open the aperture some--or if I know it's really, really bright, I might go on up to 1/2000.

For me, basically what auto-ISO does is gives me the flexibility to move straight from shooting into the blue sky at a bird in flight, to panning over to a shady, wooded section to catch an osprey landing in a tree without worrying about whether the exposure is going to be okay.

^This +1

auto ISO isn't going to fix horrible lighting, but when you have other things setup the way you like, it'll be one less thing you'll need to worry about when the action happens.

I prefer a wider aperture personally. but the limits and performance of different lenses may dictate different settings, some lenses don't perform well wide open, others are fine. most of the time I'm wide open, or within 1 stop of wide open (mostly between f4 and f5.6 depending on the setup I'm using at the time) both because I want to keep the ISO low if I can, and I like the DOF that the wide aperture creates.

 

[shadowlands]

I never use 3D tracking on birds or wildlife since every time I've tried the focus has gone to something I did not want in focus. I always use single-point autofocus and AF-C for birds and wildlife.

Ditto!!!! Same here!!!