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

Birds aren’t affected so much though vampire bats which weigh around 35g can drink upto 20g in blood and so start urinating when they feed so they can fly back home.

I’ve no idea how to Google that, and on enough lists already to try but its probably something Attenborough said so its good enough for me.