Foundation holes

While clearing earth out from under my kitchen window (which juts out about 2 feet from the house in a bay), I noticed some holes in the top of the foundation at ground level. There actually seems to be concrete blocks on top of the foundation, and the outer layer stops one or two courses before the wood for the window starts. Funny thing was, all along that line of blocks were holes, at regular intervals. It's a little difficult to tell as it has been covered in insulation, but I think the holes are just the holes that come in the blocks, ie they have not been filled. We have had a few problems with mice, so I fillied in the holes with wire wool and concrete.
Were the holes there for a purpose? Will I have done any harm in filling them in? Is this where the mice could have got in?
TIA
Mat
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If the holes are cinderblock holes it sounds like the cinderblock was laid the wrong way. Holes should be on top and preferably filled with concrete.

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