These past two months, I have discovered two birds in my home. Not exactly sure how they gained entry into the house, but it is rather weird. Luckily, I was able to get them out without them paying with their lives.
The first trespasser was a mere Sparrow, last week I found a Starlett.. Very strange indeed.
With the sub-zero temperatures that we had around that time, they were likely looking to get out of the weather and you had a perfect opening in the house somewhere for them to exploit. Look for a nest or a small warm area that could house a nest. Or worse, look for a food source that could be right in your house. Food attracts critters.