General Question

andrew's avatar

How much energy do birds expend while flying? Is there a comparable human exercise?

Asked by andrew (16198points) July 12th, 2009

I, as many people do, fantasize about the ability to fly. Then I remember that for most creatures it’s a fairly strenuous activity. Does your average sparrow expend as much energy as, say, an olympic level athlete? Or is more like taking a long jog?

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17 Answers

The_Compassionate_Heretic's avatar

I would imagine the energy exerted was proportional to the flapping of their wings. It probably takes a significant amount of energy to take flight but once they are airborne at a good cruising level and gliding, it’s probably easier to maintain.

The geese flying overhead in formation is probably like jogging while the pigeon constantly taking off and landing is probably like windpsrints.

This is all conjecture as I am not an ornithologist.

andrew's avatar

Ok, for purposes of discussion, I’m not talking about gliding. I’m talking about flap flap flap get your body in the air. Also, for purposes of discussion, let’s leave those darn cute little hummingbirds out as well.

The_Compassionate_Heretic's avatar

I’d lean more towards the olympic athlete level because wild animals are in better shape than humans for the most part as it is a necessity to survival.

marinelife's avatar

And, Andrew, you have missed out on the best part of being a bird. The expression “he eats like a bird” is very inaccurate.

“Hummingbirds eat about every ten minutes, slurping down twice their body weight in nectar every day. Most birds eat one quarter to one half their body weight in food daily.” Source

Can you imagine? A 150 lb guy could them pig out on 37½ to 75 pounds of food a day!!!!!!

AstroChuck's avatar

@andrew- What do you have against those darn cute little hummingbirds?

augustlan's avatar

I’d say it’s even more strenuous than an Olympic level athlete. As Marina pointed out, birds must eat an enormous amount of food in order to expend all that energy. I don’t think Michael Phelps eats half his weight in food every day, high or not!

nikipedia's avatar

The average cost for migration days is 130 kJ, of which 71.3 kJ is spent on flight alone; the remaining 24 days are stopovers where an average of 88 kJ d-1 is expended, assuming an ambient temperature similar to that in central Illinois.
from: http://www.nature.com/nature/journal/v423/n6941/full/423704a.html

The article says elsewhere the average body weight per bird is 30g, so let’s convert to kg and divide:

71.3 kJ expended flying per day / 0.003kg = 23,767 kj/kg expended per flying day

On a flying day, they fly for about 265km, so let’s convert again:

23,767 kj/kg / 265 km = 90 kj/kg/km

This article estimates that running at speeds up to 22km/hr uses about 1 kcal/kg/km, so let’s convert our flying number to kcal:

90 kilojoules = 21.5105163 kilocalories (says google)

So our birds are using about 22kcal per kg to fly each kilometer, and a person uses roughly 1kcal per kg to run a kilometer.

augustlan's avatar

<bows before niki’s giant brain>

nikipedia's avatar

Aw, shucks! Don’t make me blush. :)

evelyns_pet_zebra's avatar

<starts a new religion to worship niki’s giant brain.>

Darwin's avatar

But what about Evelyn?

marinelife's avatar

@nik You take me breath away! Lovely!

@evelyns_pet_zebra Oh, faithless one!

andrew's avatar

@nikipedia That’s great! Exactly what I was looking for!

Now… are there any human physical activites (even for 5 minutes) that would compare?

Would flying be the same, as, say… making pancakes? For 5 minutes?

marinelife's avatar

What about lifting the equivalent of one’s body weight?

bpeoples's avatar

@andrew looks like the peak acceleration part of a 30m sprint is about double the flight power at 45kJ/kg per http://jeb.biologists.org/cgi/content/abstract/208/14/2809

Average during a 30m sprint is still only half the energy at 10.7kJ/kg.

PrancingUrchin's avatar

I was looking of niki’s calculations and it seems that it may be off by a factor of 10. She says that the average body weight per bird is 30 grams which equates to 0.03kg not 0.003 as was stated.
Given that, birds would burn about 2,376.667 kj/kg per day instead of 23,766.667. Assuming that birds do fly 265km per day, they would burn 8.969kj, or 2.144Kcal.
Essentially, divide by 10 and you’ll get your answer. Please correct me if I’ve done something wrong.

SmashTheState's avatar

Because of the square/cube law, you can’t do a direct comparison. Trying to scale humans down to bird size, or birds up to human size, would produce nonsensical results because of non-scaling constants like the tensile strength of bone and the difference in efficiency between fast-twitch and slow-twitch muscles.

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