American Robins do winter in the Anchorage area. They eat berries in addition to worms. I don't know about seeds, but it would depend on the type of seed. You can also supplement it with dried mealworms which are usually for sale at the bird feed store. I buy mine at a farm supply store.
Robin's are normally seen in spring here in Anchorage we see Robin's in the winter as some do find warm places as long as they get food there should be no problems
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