dsims1960 wrote:
Hopefully I posted my message correctly this time. LOL. I see so many other photos that people take and they are so plan and sharp. I was just wondering what I could do. I have the Nikon d5600 and used the sigma 150mm-600mm lens for these pictures
You posted the images exactly as needed. Thank you. Below are an analysis of the EXIF data as a basis of discussion. For the two I looked at, as well as the third example, the most pressing issue is to get closer to the subject. All the exposure parameters are exactly / almost exactly as I'd use too for similar subjects.
When comparing your images to others, you need to recognize some / most / all these technical aspects apply to their work:
1) They were physically closer to their subject.
2) They had a longer effective focal length for their lens, even longer than your longest 600mm.
3) They captured in RAW.
4) They had a higher resolution camera than your 24MP D5600.
5) They processed their images using the most advanced software and sharpening / noise reduction techniques.
6) They increased the pixel resolution of their images on their computer.
7) They used overall sharper lenses, such as primes. And / or, they identified and used the sharpest overall aperture for their specific lens used.
8) They used some of the lighting ideas presented by BassmanBruce, above, such as having the sun positioned behind them so the subject is well-lit and facing into the light when facing directly toward the camera.
As said, everything about your settings are appropriate for sharply focused and well-exposed images. Your example results show these well-considered settings in practice. Now, work on your physical approach and subject selection so that you are closer to your subjects. Find a good location with lots of action and sit and wait patiently for the wildlife to arrive. It might take an hour. It might take 4 hours.