Complex sentence: Locally, eagles may rely largely on carrion, especially in winter, and they will scavenge carcasses up to the size of whales, though it seems that carcasses of ungulates and large fish are preferred.
Split into simpler sentences: Locally, eagles may rely largely on carrion, especially in winter. They will scavenge carcasses up to the size of whales, though it seems that carcasses of ungulates and large fish are preferred.