They say you should should only photograph using RAW images but I have not put any effort into learning the processing packages. A recent picture of a Juvenile Fiscal Flycatcher had bad contrast and lighting, It was ideal for post-processing using DarkTable. The result was pleasantly surprising. Here are the results of my initial efforts. Probably with more practice the results will be better, but I am quite pleased with what I achieved.
This is the original pictures. Note how little detail is visible on the back of the bird and how the colours are muted.
Here is the same picture after processing. The difference is quite marked.