She picked one of the line of sparrow-speckled mice for this, so it will look all matchy, if it comes through. She tends her sparrowmouse carefully.

Her sparrowmouse seems pretty confused and curious about its new wings! Then it gets bored with them; they're still useless. 

A week in, the nerve grafts heal enough that the sparrowmouse can twitch, twitch, twitch the wings. It's very uncoordinated, though; its brain does not have a spot for 'wings' and it must be baffled as to what they're for. 

The book describes a technique for aiming some Healing-energy at a creature's brain, which is supposed to give it more ability to learn new things than an adult of that species usually could. It's also fiddly, though, and can cause the animal to instead get a tumour in its brain and die if it's not done quite right. 

Seems best tried on non-painstakingly-grafted mice first. She will teach green mice tricks as a control and blue mice the same tricks with bonus brain energy.

The first batch doesn't have much difference, she must not have gotten the hang of it, but the second batch learns noticeably a bit faster. One of them gets a fast-growing brain tumour of some sort, though. The third batch does even better with tricks and she doesn't give any of them cancer either. 

(Her winged mouse seems to be making some headway, its wings are less randomly spastic, but it's definitely not learning flight.) 

When the third batch has learned to walk tightrope and run little obstacle courses she will try the brain trick on the sparrowmouse.

(Leareth is rather delighted by her tightrope-walking mice.) 

The sparrowmouse is definitely more lively and playful! It spends more time flapping its wings around and trying things with them, but it doesn't seem to have occurred to it that the thing they're for is flying. Maybe it needs to be taught more explicitly. 

What happens if she sticks it right next to the sparrows?

It's very curious about them! Also pretty wary. It spends some time gradually getting more comfortable sitting right up against the sparrow cage and watching them flutter about. 

After a while, something seems to click, and instead of playfully jumping or attempting to burrow into its wood chips (which goes less well with wings), it also adds some playful attempts to leap and flutter. 

She could try putting some food at a place it can't reach without some fluttering? 

Yup. Treats up on a high shelf in the cage, suspended from the ceiling so it can't just climb.

The mouse is now a lot more determined! It watches the sparrows intently, and tries jumping and fluttering, and is not very good at staying aloft or steering and bumps into the bars some, but within a few days it can get its treat with multiple attempts, and two days after that it's a pretty good flyer. It's not quite as adroit in the air as the sparrows, maybe because it's starting in adulthood and the brain-Healing can only compensate so much, or maybe because its mouse body just isn't very aerodynamic. 

It's encouraging! She will make it a sparrowmouse mate and see if they have sparrowmouse babies.

Sadly they don't. Some of the babies are normal and some of them have some minor deformities, but not wings. The book did warn that this part was a lot harder to master. 

(The two sparrowmice get along well, though, and are very adorable in their cage.) 

She will persevere at getting a breeding population of sparrowmice out of intellectual interest even though she is not actually planning on this being a major feature of her own future body; it's good practice.

It's taking a while.

Leareth is noticeably growing now! He's taller and his voice is just starting to break and he informs her that some other signs of puberty are starting to show up. His face still hasn't lost any of its baby fat, though, and so he doesn't look older so much as bigger. 

"I don't know if I can speed this process up by attempting to become sexually attracted to you on purpose or not but at some point - maybe not yet - that'll probably make a few months worth of difference."

Nod. "Maybe not yet. I assume at some point I am going to start having - feelings, about that sort of thing, I have not yet. I can tell you when that happens?" 

"Yeah." Sigh. "I miss how you used to look. Even when you're physically twenty or whatever..."

"I am sorry." He looks thoughtful. "I - could probably shape my adult appearance somewhat? Well, you could, mostly. Once you have done some more experiments on mice and can definitely do so safely." 

"There's an idea. After I'm a lot better at this, but I'll get there."

"You are making very rapid progress." He looks so delighted about it. 

"The sparrowmice are cute! Impractical, but good practice."

"If you are able to get a breeding population, you could probably sell them as pets. I think children would adore them." Frown. "They might become terrible pests? Although I suppose they are likely to be somewhat fragile. Gryphons are, they have all sorts of weird medical problems. I went back and read one of my books on them." 

"Oh dear. What kind of weird medical problems?"

"The ones I recall off the top of my head are that they run into serious difficulties with their flight feathers if they do not have someone to help clean and oil them - birds can reach all of their own feathers, but gryphons' bodies are not flexible enough. They have frequent problems with the oil glands too, and I think their digestion is known to be finicky? I am not sure why the wings affected that, but perhaps the bird and mammal components were adapted for different diets, and the intermediate digestive system is sort of worse for either."