Starting with your organic intersections, here you've done an excellent job of establishing how these forms interact with one another in 3D space, as well as of capturing how the shadows are cast from one form onto a variety of curving surfaces. As a result, the relationship between the forms feel quite solid and believable.

Moving onto your bird constructions, the first thing that stands out is that you're drawing with what appears to be a two-stage process - first you put down your big masses (usually a series of ellipses) more faintly, and then when you feel more sure of what you're after, you go back over their silhouettes, committing to certain strokes (at times with some small adjustments and modifications) with a sort of clean-up pass.

This is not how you should be approaching your drawings within this course, and it's actually something I addressed, at least to some degree, in my critique of your lesson 4 work. There we talked about the importance of not altering/extending/cutting into the silhouettes of the forms you'd already drawn - instead treating every single form as being a solid entity within the 3D world, and ultimately building additively upon them in order to develop greater complexity.

Tracing back over parts of your construction unfortunately often leads to this kind of a mistake, and as a result flattens out the drawings. This is usually due to a misunderstanding of how line weight itself works, and how it should be applied. Line weight serves a very specific purpose - it clarifies the overlaps between forms in limited, localized areas. It's not used to assert a new silhouette (because that would involve adding 2D information, rather than building up the construction purely using 3D forms). Instead it follows over a limited section of the existing silhouette of a form, and avoids getting too long. As long as we keep it limited in this way, we don't risk getting into the territory of redrawing and changing those silhouettes.

As discussed back in Lesson 4, it's extremely important that you always think about how the forms that you're adding are to interact, intersect, and relate to/with those that are already part of the existing structure.

As a whole, you're definitely somewhat too relaxed in where you're willing to let yourself slip back into drawing with 2D shapes, rather than keeping everything solid and three dimensional. For example, with this capybara's head, there's no actual defined relationship between the cranial ball and the animal's muzzle. You drew the muzzle farther forward, and then bridged across using flat shapes (extension of silhouettes). Instead, it's pretty important for the solidity of the structure for that muzzle to come straight off the cranial ball, and to more clearly define how they intersect.

You can see this demonstrated further in this explanation from the informal demos page. Now this is something you improve upon to varying degrees - for example, this lynx's head shows a much better defined relationship between the muzzle and the cranial ball. Still, you are a little loose in how you're defining the eye socket, and I would strongly recommend that when doing these kinds of constructional exercises, that you more clearly define the eye socket with a sort of upturned pentagon, cut with relatively straight lines, so there's a nice wedge for the muzzle to fit into, and a flat edge for the brow ridge to be placed upon as well.

Another minor point - you don't appear to be placing a simple contour line at the joint between your leg segments to help define the relationship between those forms, and you also don't appear to be completely sticking to the sausage method (sometimes slipping into drawing ellipses instead of sausages, like in your hippos). You should probably review the specifics of the sausage method.

The last thing I want to call out is that you should always reserve your filled areas of solid black for cast shadow shapes only - that specifically means that if you can't pin down the specific nature of a particular form which is casting the filled black shape you wish to draw, then you shouldn't draw it. Cases like filling eyes with black, and the arbitrarily filled tufts of fur on the mountain goats should both be left alone. No capturing local colour (like things whose surfaces are actually black), and no capturing any sort of form shading. Keeping our filled blacks only for this one purpose will help make their role in our constructions and our capacity to communicate visually with them that much stronger.

Now, as a whole your drawings are quite good, and there are some rather complex spatial problems that you've solved really remarkably here (like the open hippo mouth). That said, you are a little too selective in where you're opting to follow the principles we espouse in this course, and where you're letting yourself take little shortcuts. As such, I'm going to assign some revisions below for you to demonstrate that you can stick to these principles of strictly additive construction, using the sausage method, etc more consistently.

You are absolutely capable of this - it's just that you fell off the path a little bit.