Nectaring Intensely Focused Feeders Monarchs must hurry because they must eat enough nectar during their journey south. People can help monarchs during fall migration by providing nectar sources. A butterfly garden can be an important place for a monarch to refuel. This line graph shows how much fat a typical monarch has each month of the year. The nectar monarchs eat in the fall fuels their migration. Extra nectar is stored as fat for winter survival.