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
Note that birds spend a lot of time not flying. They can just have a nap if they want to. Documentaries and factoids seem to imply that birds like hummingbirds are incapable of rest, and must eat 24/7 to avoid starvation, when in reality, they only need to do that to maintain their energy consumption while flying.
There are many different “styles” of flight among birds as well. These allow birds to avoid spendig extra energy. Large seabirds like the Albatross have evolved to be able to
fly with very little effort, and can stay in the air without spending much energy for a very long time. This comes at the cost of havin a difficulty time taking off on short notice. Parrots meanwhile, are optimized for dense forests. Although they are inneficient flyers, they can maneuver quite well, take off with little effort, and can use their beak and claws to climb trees. They perfer to fly in short bursts rather than going long distances.
Their bones are structurally different from ours. They have hollow bones, which helps them twofold; to reduce overall weight and to store oxygen in their bones. And feathers make a bird (or animal in general) seem bigger than they are, you look at a bird and deduce from their size that they seem heavy while even the biggest owls only weigh around 2-5 kg.
Birds eat as much relative to their stomach volume allows, therefore the common mistake of giving breadcrumbs is actually bad for avian animals. They have to be really efficient with their food intake, and bread is neither good nor bad for you. As it lacks essential fatty acids and many amino acids, this is equivalent to them eating donuts all day (rich in calories, low in essiential building blocks of life). Fine on the short term, bad for longevity. They have to carefully find their correct food supply, or they will not be able to fly (bread lacking the fat content to ensure the feathers with enough oil for aviation) and other complications.
You are thinking that constantly eating means they have to carry around more weight, but actually this is backwards. Constantly eating means they have to carry around less weight.
Consider two hypothetical birds. One eats ten percent of its body weight once per day, the other eats one percent of its body weight ten times a day. Same amount of food, but one is eating constantly and the other isn’t.
The bird that eats 10% of its weight once per day has to carry around a whole extra 10% right after eating. As it digests this food and burns it/eliminates wastes, it’s weight slowly drops down back to normal. But it spends time carrying around a lot of extra weight. The bird that eats 1% of it’s weight 10x a day, on the other hand, is never carrying around more than 1-2% of extra weight, and maybe not more than 1%. It’s burning and eliminating wastes as it goes, so the weight doesn’t build up.
By eating all the time, birds distribute their mass intake across the day and avoid getting heavy at any one point in time. Exceptions are birds like vultures, which somebody else mentioned, that have to take in big meals periodically because of their particular ecological situation.
Birds are incredibly efficient with their energy and have very high metabolisms. When they eat, their bodies quickly convert food into energy, so they don’t carry much extra weight for long. Their lightweight bones and strong muscles help them fly even after a big meal.
They also poop a lot. Bird digestive system works fast and they don’t store their poop like we do, they get rid of it quickly.
I have a pet bird (Wood Pigeon) and when he eats he poops, a lot.
Still, he’s quite a chunky bird and can fly despite that. They just evolved this way. Their feathers often weigh more than their skeleton, they have very strong muscles for the wings, and it’s more beneficial for them to load up in a single sitting than to be vulnerable more often by eating less but more frequently.
They also only need energy for flying when they’re taking off, accelerating or changing direction. Once they get to a decent altitude they can glide on open wings for long distances without using much if any energy.
Haha , when I was in Alaska you can see this effect on the puffins . They eat too much and have trouble taking off , a bit hilarious .. they are all right after awhile … but sometimes they just flap and skim the water and settle back down and wait till they digest a bit more 🙂 not sure if it’s due to weight or whatnot , not very scientific of me to think this is what actually happens , but it’s fun if it’s really due to over eating
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