In Fennoscandia social groups of Crested Tits & Willow Tits defend carrion against other groups, so must be some benefit, at least sometimes. E.g. boreal winters when seed are scarce it could be important resource. Maybe not vital to persistence/extinction, but an ecol link, like boars/robins in UK.

Yes I agree, it’s clear carrion can provide corvids and, to a lesser extent, some small birds with some benefit in winter. When thinking about restoring ecosystems we need to be clear that any such short-term benefits may not translate to apex predators having overall or net benefit to small birds.