This feat is impressive, as an 800 km (500 mi), non-stop flight over water would seemingly require a caloric energy that far exceeds an adult hummingbird's body weight of 3 g (0.11 oz).[21] However, researchers discovered the tiny birds can double their fat mass in preparation for their Gulf crossing,[25] then expend the entire calorie reserve from fat during the 20-hour non-stop crossing when food and water are unavailable.

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