Probably dumb as a box of rocks. 
you say that like nobody knows that- im writing from the perspective of a sci-fi writer who goes overboard on my space critter classficcations when i make them
What did you mean by that??
In that case, Japanese Coturnix would be classified with peeper frogs and similar frog and toad species! What a cool thought!
Edit:
Whether aliens exist or not, it’s still pretty fun to think about how they would interact with the wildlife many of us love and study, on an amateur or professional basis! :-D
Dang, I love being childish, don’t y’all agree?
Hahahaha, in our imaginations they do.
i mean that you answer the post as if scoffing at the idea of aliens, which is pretty clear that there is no evidence of their existence, but this is a hypothetical question, of if they did exist. as a sci-fi writer, i like the idea of aliens, but have no belief in them being real- like how im also a fantasy writer.
Really? You write books? What kinds of fantasy? Romance, history/fiction or what?
Your a sci-fi writer? That’s so cool!
I have an entire sci-fi universe I’ve created based on drawings I’ve done.
Omg awesome! Could you please show me some tips on how to write a good story? I’m very interested in writing a story.
Do you have any tips on drawing/sketching?
Sure, I can give you some tips if you want, but this is probably not the place to discuss them. You can message me, though.
I have some tips too, and also on writing.
Message me; I don’t want to clutter up this thread.
im not published or anything, but i have several projects actually- ive got a space war sci-fi, some high fantasy, cyberpunk, a couple romance, and a weird time travel thing
message me on discord for more information if you like, since this forum is for nature-related conversation tho- forestbeans_87000
If they’re capable of reaching Earth, then they may be able to specifically determine the genetic structure of every specific individual, and possibly do this via some kind of orbital scanning.
So I think they’d classify Earth lifeforms by their precise genetic structure, and therefore their precise relationship to every other lifeform ;)
A phylogenetic tree, that includes every single organism (and I guess non-organisms, like viruses and transposons…)
I imagine that aliens drawn to earth for planetary exploration would be attracted here by features that make life possible and/or are generated by the activity of life on earth. Primarily that would be our oxygen atmosphere, which should be detectable from far out in space acting like a beacon to any space-faring aliens.
So I could see their first crude classification of life forms on earth being two major groupings: produces oxygen (primary producers capable of oxygenic photosynthesis) vs. does not produce oxygen. Plants, algae, cyanobacteria would end up in the first group, animals, fungi, and most other microbes in the second group. If they are seeking to exploit earth’s resources, they may assign higher value to primary producers making oxygen than “competition” in the form of consumers.
Another thing of importance/value to them may be the presence of large amounts of water covering earth’s surface. So I could see the next round of classification be based on that. They may group things into living in water, vs. living on land, vs. airborne.
Maybe at this point they’d be close enough that their sensors will pick up that some lifeforms produce heat (endotherm) while others don’t (ectotherm), and some move around, while others don’t resulting in the old classification scheme of botany vs. zoology as organisms that are sessile vs. mobile.
So now they have life on earth grouped into:
- Photosynthetic, in the water, mobile (phytoplankton)
- Non-photosynthetic, in the water, mobile (swimming creatures, separated into endotherm vs. ectotherm)
- Photosynthetic, in the water, sessile (large algae like kelp)
- Non-photosynthetic, in the water, sessile (corals etc.)
- Photosynthetic, on land, sessile (plants, lichens)
- Non-photosynthetic, on land, mobile (land animals, separated into endotherm vs. ectotherm)
- Non-photosynthetic, on land, sessile (fungi, soil microbes etc)
- Non-photosynthetic, aerial (all flying creatures, separated into endotherm vs. ectotherm)
They could probably do all that just by scanning earth from space and interpreting the chemical and physical signatures of life on the planet before they even got a glimpse of what any of the creatures here look like.
Wow! That was well thought out.
Well, I’m nerdy enough to have a Starfleet uniform in my closet somewhere so of course I had to give it some logical thought. 
Unfortunately I could see a dry separate wiki for hominid or something,
with ethnicity tabbed, why were they under observ would be more important I agree