To my eye the problem is the jay is competing with the sky and a distracting background. Cropping in on the jay increases its presence, which is part of my suggested answer. Making the background less distracting also helps, which I did by selecting it and softening it with negative clarity and negative sharpening and lots of denoise.

The jay is also competing with the brightness of the sky and background. Reducing their highlights takes some of the edge off of that, plus lifting the shadows gives the jay a needed lift brightness-wise. The rest was playing with brightness levels, contrast and colour strength/brightness. I avoided desaturating the background because that would have left the overall image a bit bland. I also avoided cropping in too close because it emphasises the soft patches on the jay's feathers.
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This is a highly cropped version of a jay in a tree in my back yard. As I view this, the only reaction I have is "bland." No "pop." (I worked with a fine art photographer for several years who once told me: "'Pop' is not a photographic term. Analyze the image and decide what it is lacking and then fix that, e.g. sharpness, saturation, etc. etc.")

This is almost a monochrome image, since the yellow-green is dominant. What can be done without adding any extraneous elements to give this a little more appeal? Color grading?

I want a straight photograph, and not an abstract or some such, but I want something more than you see here. Feel free to edit with your suggestions...