Ask Mr. Smarty Plants

Your question has been forwarded to the Canadian Green Guru because I live in an ecozone very similar to yours on the Eastern Shore of Georgian Bay.

The shrub that comes to mind first is Sambucus racemosa var. racemosa (Red elderberry) because it is quite common in this area and has clusters of red berries on it right now.  It was blooming back in May/June. The other elderberry native to your area, Sambucus nigra ssp. canadensis (Common elderberry) is flowering now and will have purple berries later in the season.

If you visit our Native Plant Database and do a Combination Search for Michigan, selecting shrubs and part shade to shade (light conditions in the woods) it will generate a list of shrubs that fit that description.  Each plant on the list is linked to a detailed information page with images.  You can look through those and see if you find your plant.  Not many on that list have "large clusters of small red berries", but a couple of other possibilities are:

Shepherdia canadensis (Russet buffaloberry) This plant should have red berries on it now, but they aren't really clusters.

and

Viburnum lantanoides (Hobblebush)  This plant is not native to Michigan but is to Central Ontario, so it could very well be present in your woods.  The leaves are significantly different from those of the elderberries' and it usually doesn't have berries on it until later in the summer so you should be able to ID it from the images.

Of course you have piqued our curiosity, so please let us know if you can identify it.