I’m particularly drawn towards the minimalist photograph of the birds. However let’s start by discussing your first photograph.
This assignment asked that you showcase your ability to see in tones rather than colors. It also asked that you find both a photograph with a wide tonal range and another with not only tonal range, but uneven tonal balance.
What I like about your photographs is that they are tonally opposite to one another. Your first image is unbalanced towards the left end of the spectrum (blacks) while your second image is unbalanced towards the left end of the tonal spectrum (whites).
Your first image used the fur of the animal to act as textured negative space. This keeps the photograph organized and simplified. However, the fur of the animal ensures that the negative space isn’t “dead space”. It’s still highly textured and useful to the photograph. It also serves the purpose of ensuring you have a low key (i.e. dark) photograph.
Your high key photograph is spectacular. I really love the image of the birds. Again, you’ve used the sky to act as your negative space, but there is tonal gradients in the sky and clouds which ensure the backdrop for this photograph isn’t seen as oversimplified or boring.
My only recommendation for you would be to experiment with your photographs gamma settings. You can sometimes do this in your camera, but if not, it’s a common function in post production software such as PhotoShop. What this will allow you to do is “crunch” your blacks which deepens the richness of the dark-tones (often without effecting your lighter tones) and this helps give your image a really crisp look.