Fascinating! Though how much of that would be due to a birds baseline metabolism? Wouldn’t be a fair comparison if that includes the birds basic energy costs of living.

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nsarrazin an hour ago | parent [-]

Did some quick maths, it’s roughly 10% for the bird (2W, approx. 4g/day of fat, over 10 days) so not negligible but doesn’t change the full story.

And you could argue the plane also has a baseline metabolism ;)

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timcobb 40 minutes ago | parent [-]

Haha thanks for the check, I am, tbh, pretty surprised. But it's within the same order of magnitude given the assumptions, which is interesting too.

	▲	nsarrazin 25 minutes ago \| parent [-]
		To be completely fair to the birds, I think a lot of this comes from the fact that what matters for flying efficiency gets better as you size up thanks to the square-cube law: the drag is reduced and the engine efficiency increases. You could not scale down a plane to the size of a bird and match their efficiency. On the other hand you also couldn’t scale a bird to the size of a plane so I guess we can call it even!