Why do hummingbirds store fat rather than carbohydrates as reserve energy supply before crossing the Gulf of Mexico?

Hummingbirds store fat rather than carbohydrates as their reserve energy supply before crossing the Gulf of Mexico because fat provides more than twice the energy per gram compared to carbohydrates, making it a more efficient fuel source for long flights. Additionally, fat is less water-intensive, which is crucial for these birds during extended periods without access to food. This adaptation allows them to maximize energy storage and sustain their high metabolism during migration.