I want to thank everyone who responded to my question. Based on several recommendations I have purchased Steve Perry's book on the Nikon AutoFocus system. I am putting on hold any decision about new equipment until I have improved my knowledge of the autofocus system. As always, this forum has been most helpful!

It did not attach properly - I will try again

First, thanks to everyone who has taken the time to respond, I really appreciate your insights. As to the questions above,
1) I take pictures for the sheer enjoyment of both the challenge involved, and the opportunity to see a side of nature that I cannot otherwise see.
2) My budget is about $2K.
3) My version of the 70-300 is about 3-4 years old, it does have VR but is not the newer "P" style.

I have included below a copy of an instance where the BIF image actually did work reasonably well. The conditions of the camera and lens I think were similar. I think one big difference was the amount of light available in this image was much more than the first (further back in the discussion). Perhaps that is part of my problem, namely not appreciating the extent to which the amount of light available influences the quality of the autofocusing.

Thank you all for the helpful advice. I have attached two photos I took yesterday of a small green heron. The first is him perched on a structure. Not the greatest photo, but reasonably in focus. The next picture, a few seconds later, is after he took off. The heron's distance from me is almost the same as a moment earlier, yet the heron is completely out of focus. General conditions: Focal length - 300mm; Focus mode - AF-C; AF-Area mode - Dynamic, 9 points; VR on; Aperture - f/5.6; Shutter speed - 1/4000sec; Metering - Matrix; Exposure mode - Aperture Priority; ISO - 2000; Hi ISO NR - on.

When the lens tries to focus I hear a "mmm-mmm" sound of the lens trying to lock on to the subject. It almost always does correctly after a few seconds, so stationary subjects are fine, but if the subject is moving, its has difficulties.

Ultimately I try to set up the camera to have a shutter speed of 1/500 sec or faster so the BIF is not blurred. I also try to keep the ISO as low as possible to reduce the noise in the image. So I typically I set the aperture to 5.6 (the largest for this lens) and set the ISO to as low a value as possible that still produces a shutter speed of 1/500 sec (or faster). Auto focus set to continuous (AF-C). WB set to Auto. I hand-hold the lens. I am not sure if this is ideal, so any suggestions would be welcomed. Thanks!

I use a Nikon D7200 and a 70-300mm AF-S lens for wildlife photography, especially BIF. The results have been fair at best, as either focus is not achieved quickly enough, or the background, not the bird, is selected as the focal point. I can either upgrade the camera or the lens, but I don’t have the money to do both. It seems like my best option is either moving up to a D500 or a 300mm f/4 PF. I have done much research on both, but real-world experience from more experienced photographers is always invaluable. Can anyone recommend the lens or the camera as the next logical upgrade? Thank you in advance.

From what I understand the major manufacturers (e.g. Canon, Nikon, etc.) will only repair equipment that was purchased in the country it was originally destined for. If I purchase used camera equipment from overseas through eBay and at some point in the future it needs repairs, am I out of luck or are there ways to get it repaired?
Thank you in advance for your help - I really appreciate it.

I do mostly wildlife photography and use a Nikon D3200. My go-to lenses are a Nikon 40mm Macro lens for insects and flowers, and a Nikon 70-300mm for birds and other distant animals. I don't often have the finances to upgrade, so I need to make good choices when I do. As I consider my options based on the kind of photography I do, it seems my best choices now are either to upgrade my macro lens to one with a longer working distance (such as the Nikon 85mm macro) so I can be further away from my subjects, or upgrade my camera to a Nikon D7200, since the cost of both is similar right now (better telephoto lenses are way out of my price range, so that is not an option at this point).
I think I have a pretty good idea of the improvements I will get from the 85mm lens, but I am less clear what type of improvement I can expect in going to a D7200. I have read reviews that indicate there is a substantial improvement in going to the D7200, but it is not entirely clear to me how the improvements will flesh out. I would appreciate any advice people can give me regarding whether choosing a new lens or a new camera will provide a bigger improvement for my photography. Thank you all in advance for your input, and for taking the time to read this post.

My question is how to prioritize adjusting shutter speed, aperture size, and ISO setting. I like to photograph wildlife but I live in an area where cloud cover often limits the light I have to work with. From my understanding a large aperture will enable a faster shutter speed at the expense of depth of field, and high ISO settings will enable smaller apertures for better depth of field but can introduce higher noise levels due to the increased gain required on the signal from the CCD. So I am wondering if there are some tried and true maxims that experienced photographers use to prioritize which they adjust first. For example (these are completely made up) "Your eye is better at determining focus than your hand is able to hold the camera still, so reduce your shutter speed first" or "Always increase the ISO first". If any such rules exist or if people have advice on prioritizing settings I would appreciate it. Thank you in advance for your responses.

Thank you all for your help! I appreciate you taking time out of your busy days to respond. I have learned a lot and I am looking forward to putting all these suggestions into practice.

Thank you!

I am using a Nikon D3200, primarily with a Nikon 70-300 telephoto lens.

I am not sure if I can explain this very well, but here goes. When I look at grass or trees my eyes see "green", but when I look at an image of them taken with my camera (Nikon D3200) there appears to be much more gray coloring in it. I am wondering if there is some setting I need to adjust on my camera, or is there something wrong with my camera, or is the image correct, and my brain is just naturally filtering out the gray color when it thinks it should see green?