Can you post an example or two of your images?

Bird photography is fun and rewarding, but it has it's challenges.

As I read your post, you may have three categories of concern - learning the camera and lens, learning composition, and learning post processing. All three go together to make good photography.

What I have found that works for photographers in your situation is to join a local photography club. There you will likely find at least one person who does bird and wildlife photography. Many club members are either guys (and gals) like yourself, serious enthusiasts or retired professionals, and in general are very happy to share their knowledge.

Before you go out and splurge any more money on tripods or gimbal heads (not pan tilt, which will be clumsy to use), that could cost you as much as your lens alone if you do it right, consider using you camera and lens hand held. It has wonderfully effective stabilization that will get you usable results at extremely slow shutter speeds like the cat image below. I have a remote release, which I have attached to my camera for birding just a handful of times over the years. It's better to learn good long lens technique if you are using your camera on a tripod. It's best to have "full contact" with your camera and lens - this way you can dampen vibrations with our hands and face. You might find this helpful:

https://www.youtube.com/watch?v=n8HVPrPzpR4

The other images is a sampling of the kinds of images I have recorded, and all were hand-held.

Your lens is not that different than the one I used for these. It's a little longer and a little slower but still very serviceable and there is no reason why you can't realize your goals with your new gear. For now, as others have suggested, put the 1.7 TC away, and concentrate on your technique. Rather than rely on focal length, try and get closer to your subjects whenever you can. With larger birds, sitting in your car is a great alternative to a blind. Birds are less likely to be spooked by a car than they would by a person.

Birds congregate in a location for food and mating - and they are not going to let a human with a camera stand in their way of getting either or both. A camo lens coat will keep your lens free of scratches and lower the wear and tear.

For birds in flight, practice with pigeons or gulls - both are in ample supply most of the year and are fairly accustomed to people.

Learn the habits of your subjects - I cannot emphasize this enough. It will help you find them and also help you get close.It will take patience and focus (no pun intended) to get you there.

When I got into digital after film I started with a D70s. That DSLR was designed for the consumer and did a lot of thinking for me. After a while it was time to upgrade so I went for the D200. That move was a shock. This camera took worse pictures than the one I was replacing, I was really disappointed. But then I came to realize that this camera was not for the consumer, it was intended for sophisticated photographers. It allowed me to make all kinds of adjustments including what to do with each image as it was taken and it was my responsibility to decide how I wanted the pictures to be taken.

It was a good six months before I was really happy with my D200 but over that period I became sold that this was truly the camera for me. Since then I got a D3 and a D800 as well and both went through the same process of making adjustments until each camera performed according to my expectations. The adjustment period was faster since I had learned from the D200 but it was still necessary. I should say too that I am still using the D200 as well, it's my travel camera.

Your D500 is not a typical consumer toy, it doesn't think for you as cameras like the D3xxx and the D5xxx do. For that extra effort however you are rewarded with outstanding images. So learn what's in your menu structure and what it does and before long your D500 will astonish you.

The other thing to consider is some software. A cheap solution is Adobe Photoshop Elements, a bit more sophisticated would be Adobe Lightroom and at the top of the list would be Adobe Photoshop. I would start with Elements so you can learn the controls and the options and master the language of digital too. Adobe products are not exactly user friendly most of time so you're in for a learning curve, Then as you become more demanding and sophisticated you can also upgrade your software. There was a limit to what we could do with film after processing. I shot slides so what I got is what I had to live with. But with digital there is an awesome variety of things you can do with an image and these tools then contribute to the overall product you produce with your camera.

Finally, keep it simple as you learn. Pick an adjustment and take pictures changing the adjustment as you go along. This will help you master each option and control. Don't be afraid to push beyond the camera's choices too, that's a way to become more creative. And note your issues, then try to find a solution for each issue. Through this step by step process you will intuitively be able to work everything and your pictures will become award winning.

Good luck!

I am also a bird photographer. I shoot with the 200-500 and have for about a year (although I use a D7200 body). This is simply a great lens. It is very sharp at all focal lengths and all apertures. I use it hand held (Nikon says 4 or 4.5 stops of stabilization). I cannot use a tripod even with the gimbal head. The 1.4 multiplier does maintain auto focus but is useless when photographing very small, quickly moving birds like warblers, vireos, etc - those that tend to hide in the canopy and hop quickly from branch to branch. The multiplier is very useful at shore birds such as Egrets and Herons that tend to stand and watch and wade after their targets. You can get some startling pix there and also at rookeries where your tripod would be helpful (I still handhold there). I do use auto focus although most pros recommend against it. With my age, eyesight and reflexes I am just not fast enough any more to be effective. I have been extremely over the 5 years that I have been birding with the AF. The D500 (and the 7000 series of Nikons) provide so much capability and variability in the focus modes and patterns (AFS, AFA, AFC - single point (moveable), 9, 21, 51 group). The shutter fire-rate and buffer size on the 500 is superb. I think I would trade the 1.7 extender for the 1.4 after all the D500 is a "C" sensor which gives you about a 1.5 crop factor. With the 1.4 and the crop factor the 500 lens becomes about 1100 mm. I agree with a previous comment about patience in birding. Also a heck of a lot of luck in sightings helps! All the best and good birding!

Wow! Talk about buying a camera/lens you can grow into! I started with a Kodak Starmite II! (see below)

There's not really too much I can add, since most people here have already given you a lot of good advice. (Note: MOST). I would agree to ditch the 1.7X in favor of a 1.4X. I also own a Kenko Pro 1.4X and 2X, both of which have their uses, but not for someone not completely familiar/comfortable with the equipment. Results will be hit or miss at best.

But I agree that if you want to get the most out of this forum, the best (most painful ?) way to proceed is to post a couple of pictures that you have been most disappointed with. Then give forum members exposure information (ISO used, f-stop, shutter speed, lens zoom focal length at time of exposure, tripod?, light level (ie: just before dark, etc), and anything else that might seem important.
Much of this information can be gathered (if you don't remember it) by a program that can read EXIF information (pertinent data embedded in the image file). My personal favorite is located here and it is free: http://www.faststone.org/FSViewerDetail.htm This is also a good batch resizing / editing program and the price is right! In spite of using Photoshop and Lightroom, I still find faststone extremely useful. The most important for me is the batch resizing option which allows me to take my large originals and bring them down to size for web publication (ie: here!). It also lets you hover the cursor over an image and see the EXIF info. If you have difficulty with this, just PM me and I can help.
In any case, when you post, you WILL get much criticism, so put your alligator skin on, but you will also get many useful suggestions that will speed up your learning process. Other than being out there in the field with you, it is your best (least expensive) chance to get individual attention from many "teachers".

Wow! Talk about buying a camera/lens you can grow into! I started with a Kodak Starmite II! (see below)

There's not really too much I can add, since most people here have already given you a lot of good advice. (Note: MOST). I would agree to ditch the 1.7X in favor of a 1.4X. I also own a Kenko Pro 1.4X and 2X, both of which have their uses, but not for someone not completely familiar/comfortable with the equipment. Results will be hit or miss at best.

But I agree that if you want to get the most out of this forum, the best (most painful ?) way to proceed is to post a couple of pictures that you have been most disappointed with. Then give forum members exposure information (ISO used, f-stop, shutter speed, lens zoom focal length at time of exposure, tripod?, light level (ie: just before dark, etc), and anything else that might seem important.
Much of this information can be gathered (if you don't remember it) by a program that can read EXIF information (pertinent data embedded in the image file). My personal favorite is located here and it is free: http://www.faststone.org/FSViewerDetail.htm This is also a good batch resizing / editing program and the price is right! In spite of using Photoshop and Lightroom, I still find faststone extremely useful. The most important for me is the batch resizing option which allows me to take my large originals and bring them down to size for web publication (ie: here!). It also lets you hover the cursor over an image and see the EXIF info. If you have difficulty with this, just PM me and I can help.
In any case, when you post, you WILL get much criticism, so put your alligator skin on, but you will also get many useful suggestions that will speed up your learning process. Other than being out there in the field with you, it is your best (least expensive) chance to get individual attention from many "teachers".