Final answer:
The sentence about the eagle and its mate foreshadows the Eagles winning the game by symbolically representing a high, secure position that is associated with victory or success.
Step-by-step explanation:
The sentence from the narrative that foreshadows the Eagles winning the game is: "To-day a soaring eagle attracted them. 'How he sails!' exclaimed Bess. 'I wonder where his mate is?' 'She's at the nest. It's on the bridge in a crack near the top. I see her often. She's almost white.'" This is a foreshadowing element because it subtly hints at a future event of triumph or success related to the Eagles, signified by the reference to their well-placed and secure nest high up near the top of the bridge.