What laws do I break if I dismantle it?
That is an interesting question. As far as I can see, legally the scooter would be considered lost property. The owner (the company Bird Rides, Inc) presumably did not put it there (some user did), and they still want it back (so it is not abandoned property).
Exact rules vary, but usually you must make a reasonable effort to return the item to the owner.
What exactly that means will depend on local laws. Sometimes there is an official Lost and found office where you can deposit or report lost property, which absolves you of further responsibility. Sometimes you may even have to make a reasonable effort to find the owner yourself.
In Minnesota specifically, probably you would have to notify the owner. Not doing so may constitute theft under article 609.515 of the Minnesota Statutes:
Subd. 2.Acts constituting theft.
(a) Whoever does any of the following commits theft and may be sentenced as provided in subdivision 3:
(6) finds lost property and, knowing or having reasonable means of
ascertaining the true owner, appropriates it to the finder's own use
or to that of another not entitled thereto without first having made
reasonable effort to find the owner and offer and surrender the property
to the owner; or
So you are not allowed to "appropriate" the scooter, without trying to contact the onwer. Just disassembling it and storing it is probably ok (but I'm not a laywer etc.).
It's not clear whether you are required to contact the owner if you don't "appropriate" the scooter. However, the official recommendation of the Minneapolis Police Department is to do so:
Lost, Stolen and Found Property Check
For other found items, please take the item to the nearest Minneapolis
Police Precinct and turn it in to the desk officer.
So to be on the safe side, you should probably report the scooter either to Bird Rides, Inc directly, or to your local police station.
Does the owner have any civil claim against me? Assume the scooter can be reassembled
If you do not damage the scooter in any way, then probably not. The only damage they could claim would be the cost of reassembly - however, a) this might be too trivial to be worth it for them, and b) you could claim you needed to disassemble it because otherwise you would not have had space to store it.
Again, to be on the safe side you should probably notify Bird Rides, Inc and ask them to collect the scooter within a certain timeframe. If you also notify them that you will disassemble the scooter if it is not collected until a certain time, I don't think they will have a claim against you later.