Generally, a nonresident alien only needs to report their US income on their US tax return. So if your spouse is a nonresident alien (note that having less than 183 days in the year does not necessarily mean they do not pass the Substantial Presence Test -- a fraction of days in the previous 2 years are also counted; also, if you are a US citizen or resident alien, you can choose to have your spouse treated as a resident and file jointly) and does not have income from the US, they would not need to file a tax return.
However, if you live in a community property state, your income is community income, which means half of it is considered your income, and half of it is considered your spouse's income. In that case, you would only report half of your income on your Married Filing Separately tax return, and your spouse would need to file a nonresident tax return reporting the other half of your income.