How can birds still fly if they have to constantly eat to have enough energy to fly? Doesn’t eating make them so heavy that they need even more energy to keep flying?

Question

When I watch the birds at the feeding station in my garden, I notice that individual birds often eat a lot at once. Doesn’t all that food make them so heavy that they need more energy/food to fly than they can carry in flight?

In: Biology

Answer 1

Some birds like vultures and cormorants can definitely eat so much they struggle to get airborne afterwards. They’re “high flight cost” birds that don’t have a large margin on their normal lift/weight ratio, either because they’re relatively heavy (vultures) or have stumpy wings (cormorants).

The spazzy little songbirds that visit your backyard bird feeders weigh almost nothing and are very strong fliers so they’re “low flight cost” birds that have a lot of extra power if need be. They can pack in as much food as they can fit and still take flight no problem.

They don’t need to eat constantly, but many birds do eat a lot for their size because their metabolisms run so high to make sustained flight possible. You need a lot of energy on demand to do that.