I'm using a mask for this task because it is non-destructive, which means if I need to undo anything, I simply choose white and "uncover" the sky image. Once you are happy with the result, you can apply the mask to save memory.
The sky is a little dark, so, using an Adjustment layer, alter the levels to brighten up the image (Fig.19).
Next add a layer mask to this Adjustment layer (like in the previous step) to hide the areas that do not need brightness adjustment, which is everything apart from the sky. I'm using a Highlight value of 154.
Using a Soft Round brush, brush on a very small amount of white across the sky area. This simulates a bloom from the sun that is outside of the picture frame (Fig.20).
Using a Chalk brush, I also rough in the twigs of the nest to make sure that it will compositionally work well with the existing picture elements.
Using a smaller brush, start to refine the details. I'm using a small version of the Soft Round and make sure to zoom into the image (Fig.21). In particular, pay attention to adding more highlights around the eye and using the Soft Round brush to smooth out the textures.
Using highlights, we can also create a sense of depth and wetness to the eye region and add in a few scratch marks that may have resulted from a fight with another wild animal. On the clouds I use an Overlay layer, a Soft Round brush and again paint in some white bloom around the left rim of the cloud masses to indicate where they are being lit from.
In order to increase the feel of this creature being of the wild, block in ruffled feathers to the back of its head and neck, similar to those found on some species of eagle (Fig.22).